I’ve found I got this error when my nextcloud admin user was different or non-existant to my samba user account, ie I had no admin user in samba. I was sync-ing users to nextcloud. Basically, the error meant nothing, except there was an issue. Sent me down dozens of dead ends. I’m not saying your issue is the same as mine, I just got that exact same error log message and the symptom was I couldn’t enable apps, the fix was to add a sambaAD user called “admin” with the same password as nextclouds “admin”. Hope this helps
Can you ping github-cloud.s3.amazonaws.com in your server’s terminal, if you can not ping this doman maybe your firewall or some reason you just can’t reach the apps server. I had this issue was because the damn china GFW blocks this sites.
when I tried connecte through a proxy server ,it’s ok.