Actually, I'm going to add something to this post because joining people's games has been an issue for as long as I've been in the Mass Effect 3 community (and bear in mind, my experience is exclusively with Mass Effect 3 on PC, so there are going to be more outside of what I've mentioned here.)
1. The current issue of being unable to invite friends to lobbies. See this thread and all other related threads.
2. EA App not having a "join lobby" button. In Origin, if you had a friend in a public or private lobby, you could join them by clicking a blue arrow next to their name on your friends list. If you didn't want someone joining your game, you could set your status to "invisible," which was used for doing solos. However, since the migration to EA App, we have lost this feature. The only way to join a private lobby in theory is to be invited to it. However, if you're in a private lobby, you can only invite someone to join the lobby from the lobby screen, which is in between matches. This makes it impossible to join a private lobby that is currently in the middle of a match. It also means that if someone gets disconnected from the lobby, they have no way to rejoin it, losing all credits and XP accrued during the match. The lack of a "join lobby" button is so major it led to some users creating a hacked version of Origin that did not force the migration because it has this feature. Did they break terms of service? Yes, but ask why they did it. They did it because of a very basic feature that is missing. If I have a friend playing CSGO on Steam, I can join their lobby by clicking the drop-down menu and selecting "Join Game". This is a BASIC FEATURE of any launcher that has multiplayer games, yet EA App STILL does not have it.
3. The post-2018 account problem. Ody mentioned this on his post, and it's a rather well-documented issue within the N7Squad community (to the point where some users will put "Post-2018 account" in their usernames.) If your account was made after 2018, trying to join a lobby hosted by an account made before 2018 can either be extremely difficult or downright impossible. I don't know as much about this issue because I haven't encountered it since my account is from 2016, but I've tried to play with plenty of people who have post-2018 accounts who I could not connect to.
EDIT: it is also impossible to kick a post-2018 account from your lobby. The only way they can get kicked is by being AFK during gameplay.
4. Invites or "join game" button presses leading to a one-time (or in some rare cases more) infinite load screen. Back when invites did work, this was something I ran into from time to time. I would get invited to join a lobby, then sit through the "joining game" screen for 30 seconds and not connect. Generally speaking the "joining game" screen is quick and doesn't last any longer than 2 or 3 seconds. If I see it last 10 seconds, I tend to alt-F4 and reopen my game. Restarting the game tends to fix this issue, but sometimes it will require multiple restarts. The fact it can happen at all is annoying and wastes time.
5. Mutually exclusive hosts. There are some people I play with whose host I am not capable of joining, nor are they capable of joining my host. Thus the only way I can play with said person is to have a third person host who we can both join. I've encountered this in conjunction with the post-2018 account from time to time. This is an issue I have run into with much less frequency however, but I have also been playing with fewer and fewer people over time so my ability to notice it has dwindled as I have consolidated friends that I play with whose hosts work well enough for me.
6. Long connect times. This is an issue I've noticed with one particular person who I will refer to as V. Whenever my friends and I play with V, we have to wait upwards of 30 seconds for them to join. This might be an issue of slow internet for V, but in conjunction with the issue of only being able to join public lobbies, this makes playing with V potentially difficult because we could be waiting for them and someone else could join and take their spot. On its own, it's an annoying issue. Combined with the join/invite not working, it's potentially disastrous.
7. Possible Linux incompatibility issue. Okay this one is based on some hearsay and assumptions, but it's an observation nonetheless with one specific person I play with, who I will denote as S. S uses Linux on their gaming PC, and frequently runs into issues where they cannot connect to people's hosts. I do not remember if their account is pre or post-2018, but the usage of Linux is unique to them (as far as I know.) They're able to work around this issue by using a VPN. I also think my host and their host are mutually exclusive, but it has been a while since I have tried playing on their host or them on my host so I could be wrong about that. There's a lot at play here, and I don't know if Linux is a potential issue, but I feel it is worth tossing that out there.
8. Internet incompatibility issue. This is a bizarre issue I ran into in 2021 and 2022 that may be the fault of a third-party ISP, but I am going to include it anyways because it made it impossible for me to play Mass Effect 3 from my dorm room while I was at university. This was the ONLY game where I could not connect to any lobby nor could anyone connect to my lobby. I could still play with other people on this internet through other services and servers. PlayStation noted the internet type as NAT Type 2, meaning it was not the most restrictive internet. I remember specifically being able to play Gran Turismo Sport, Dark Souls: Remastered, and Assetto Corsa Competizione on PlayStation 4 in addition to CSGO and Halo: Master Chief Collection on my laptop. The issue got fixed when I went on campus and used the campus WIFI instead of the residential WIFI, but the fact this was an issue at all was incredibly frustrating and inconvenient.
EDIT: remembered this one after making the original post. 9. Game Pass joining issue. A user I played with, who I will refer to as B, played Mass Effect 3 through Game Pass was unable to join any other lobby. However, they were able to host and I was able to join his host. This meant that anytime B wanted to play with someone, B could not join the lobby but had to wait for the match to finish, then everyone had to migrate to B's host. This was incredibly inconvenient for all people involved.
These are all the ones I have encountered that came to mind. I have no question that other people have encountered other issues. Especially considering my experience is almost exclusively with Mass Effect 3. I have very little time playing Andromeda, so I cannot speak to whatever join lobby issues exist there (if they exist, which would not surprise me.) If you have experience or insight with any of these issued mentioned above, feel free to let me know and add more information (or context) or even correct me if I said something wrong.
