This is really weird. I started seeing the same thing a couple of days ago, and switching Proton versions (latest/experimental, or even to wine) didn't help. I also bit the bullet of completely reinstalling the game, without success.

The common "fix" for this posted online seems to be to change your DNS server or use a VPN. I've looked at my DNS traffic, it's fine. Haven't gotten around to trying a VPN yet. (the hypothesis being that rockstar IP-banned you for some reason. doesn't make sense either, because I'm able to log in to the launcher initially)

someone (@arieljuod) on the heroic games launcher discord came up with a fix!

message link: https://discord.com/channels/812703221789097985/1210747284086849578/1210747284086849578

looks like after an update (?), the rockstar games launcher doesn't open automatically / in time anymore when you launch GTA. as a small hack, you can launch the launcher (ugh) in the background, wait a bit, and then run the game. This seems to also affect other games in the rockstar launcher, such as red dead redemption (which I don't play myself)

copying their message here for reference:

I'm don't play the game so I'm not sure if this is fully working, but I got inside the game in the story mode.

This is based on the solution that works on windows.

1. After installing the game, run it once so it installs the rockstart launcher, log in
2. Close the Rockstar launcher
3. In the game install folder, create a file called fix.bat with this content (the file has to be in the same folder as PlayGTAV.exe):

start /B "null" "C:\Program Files\Rockstar Games\Launcher\LauncherPatcher.exe"

ping -n 20 localhost > nul

./PlayGTAV.exe %*

4. Set this file as an alternative EXE in the game settings in Heroic
5. Run the game

NOTES:

• you might need to adjust the 20 after ping -n if the rockstar launcher takes longer to be ready
• you'll need to adjust the executable for RDR2 (I don't own the game so I don't know what's the executable)
• I imagine this should solve the same problem also on Mac but I haven't tried (and I don't know about other problems on Mac)