Václav, did it stop for no reason or did it stop after the last update? Have you tried disabling any 3rd party antivirus/malware/firewall/vpn? (one of them may have updated)

What Web Hosting are you using? Have you received any notification from your webhost that proceedures may have changed?

I can see the screen shot of the error and I assume this used to work (although with my upload settings I do not include the ftp. as part of the destination).