OK... That was unexpected.
Not an error on our side. Our hoster Hetzner just blocked port 8444 for everyone including us without any warning.
Seems like the port is used for crypto mining for others. See https://www.reddit.com/r/hetzner/comments/ngdraa/blocking_ports_is_not_the_answer_is_this_even/
I changed the server to port 8445 and uploaded a new version of lowsync which uses 8445. Please upgrade and retry.