F1 23 error code PM65539 persists beyond all solutions - can't use multiplayer

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@ItsKoolest wrote:

Product: F1 23
Platform: PC
Please specify your platform model: PC
Summarize your bug: When trying to join any multiplayer session, I receive an error code named 'PM65539', which in practice prevents me from using any of the game's multiplayer features that require entering a lobby. I have tried every fix I can find, to no avail, and other people reporting this issue have still not been offered concrete solutions, even ones requiring a compromise. For example, the most commonly offered solution is to disable crossplay, but for numerous people, including myself, even this has not helped.
What is your 16 digit Report Code? SJSX-JBPB-HDXE-VCSE
Can you please provide the name of your current internet service provider? Glide/Sky (issue has occurred whilst using both)
Which area is the bug/glitch in? Multiplayer
Did you have cross-play enabled? Yes
How can we find the bug ourselves? Attempt to join any multiplayer lobby
What happens when the bug occurs? I try to join any multiplayer session, and will get 10-15s of loading screen before being met with the error code PM65539 and the text "Failed to join the session. No response from host." I then have to select "Okay" and will be returned to the 'Multiplayer Grand Prix' screen.
What do you expect to see? Being able to join multiplayer lobbies

This issue and related error code has persisted in various forms for at least two game cycles now, with (to my knowledge) only temporary/compromising solutions offered, such as disabling crossplay and antivirus, none of which can be relied upon to solve the issue. The fact is that people either cannot fully enjoy one of the game's core and most popular modes, or like in my case simply cannot play said mode at all. We are long overdue an actual, concrete solution to this problem, but having said that, I will take any solution I can get so that I can actually play the game I payed for, so any help is greatly appreciated.

So far I have tried: Disabling crossplay (which has it's own issue of preventing me from even searching for online lobbies), Disabling antivirus, Whitelisting F1 23 from firewall protections, Using a VPN on both my local and foreign networks, Updating all of my drivers on multiple occasions, Verifying game file integrity, and Reinstalling the game on both my existing and a new hard drive, all as yet to no avail.

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Enable Crossplay.

Uninstall your AV - Windows Defender is sufficent. You will need to run a removal tool for the usual suspects (Norton, McAfee, Avast! etc. not an exhaustive list).

No requirement to whitelist the game; the Windows Firewall can be reset to defaults (your AV may be the issue here)

DO NOT USE VPN - the game does not work reliably with various VPNs and the use of to play is unsupported.

Post a dxdiag, ensuring your mainboard make and model is shown in the dxdiag.

Be prepared if all else fails to backup your Windows environment and be prepared to do a clean install. Because, sometimes, Windows just sucks.