New install, no syncing with Seadrive

I have just started to use Seafile:
VPS AlmaLinux 8
Seafile 9.0.10
Apache 2.4.3
Cert Let’s Encrypt
Everything seems to work fine, I can connect in a browser, create accounts and use files. I have installed the last Seadrive 2.0.26, I can log in with my different accounts, but I get nothing synced, all folders are empty. There is nothing special in the server logs, but local seadrive.log shows the same line every 10sec:
Bad response code for GET https://------------/seafhttp/protocol-version: 404.
I have no file protocol-version anywhere.
FYI, the Android client syncs fine!
Anyone could help me with a solution or just ideas?

Same for me.