If you’re runing the latest version of seafile-cli (4.3.2) on Debian you might encounter the following error in your seafile.log:

http-tx-mgr.c(653): libcurl failed to GET https://domain.tld/seafhttp/protocol-version: Problem with the SSL CA cert (path? access rights?).

This is because the client is built on CentOS where the CA certificates reside in a different location. Luckily there is an easy fix available (see https://seacloud.cc/group/3/wiki/seafile-cli-manual/) :

sudo mkdir -p /etc/pki/tls/certs
sudo cp /etc/ssl/certs/ca-certificates.crt /etc/pki/tls/certs/ca-bundle.crt
sudo ln -s /etc/pki/tls/certs/ca-bundle.crt /etc/pki/tls/cert.pem

That’s it – restart your client and it should sync again.