Every time I tried to install anything form the GOG GALAXY client, it will appear with an failure indicating Installation Failed(E4), "Disk access error occurred during installation", and the downloads would stop with a failed sign.

The error still appears after re-install of Galaxy,Running on a M1 MacBook with the latest Big Sur.

Does anyone know how to solve this?

I am also having this issue! Have you had any luck?

I just got the issue and after getting the error, closed GOG Galaxy and restarted it and when it re-opened it started downloading and installing it. Sorry I don't have a more solid solution but it worked for me so worth a shot

Yep, this worked for me as well.

I've been having this same problem for the past 2 years and haven't been able to install a single game.

Nothing I've tried works - running roughly latest Mac OSX each time I try again every 3-6 months or so.

- Tried giving GOG Galaxy full disk access in permissions
- Tried opening app as sudo user
- Tried chmod files to increase permissions
- Tried to 'open as administrator' aka right click open GOG Galaxy (an older mac trick)

None of it helps. Trying to install anything gives an E4 installation error, and as far as I can tell downloading process doesn't start. The one game I've been trying to play now for 2 years (Vagrus Riven Realms) has a bug that doesn't even allow you to get past the start menu if you download the game directly, so I'm sh*t out of luck.

Vagrus devs if you're out there, please let me refund and rebuy on Steam.