Plants vs. Zombies Garden Warfare PS3: Unable to join a session.

So, I have PvZ GW1 on my PS3, and Multiplayer works perfectly fine, but Garden Ops... Well, I can join my friends' sessions mostly, but, when I try to join other's sessions, (it's mostly set to any map for some reason lol) it doesn't really work, and give me an error:

"ERROR

Unable to join a session. Please check your internet connection and try

again."

My Wi-Fi is pretty stable, so... I don't know why it's not working... Can anyone help? 🙂

P.S: I think people can't join my sessions too...

Here's a screenshot: (also sorry for low quality but my phone was dead and i could only use my laptop's webcam xD)