sql backup never starts only backing up
Most likely reason is that the necessary ports are blocked.
Check against the followin article to see which ones must by open -> https://kb.acronis.com/content/47189
Test the connection using the Connection Verification Tool (reference article -> https://kb.acronis.com/content/47678) and share the output here. Note that if you have strict firewall rules with Deep Packet Inspection, normal connection would go in and out just find, while SSL connection would be intercepted.