You have registered an account and specified your backup storage (Partner-owned backup storage). You have registered a machine in that account and run a backup to the specified storage. Later, you have changed the storage in the account settings and removed the old storage.
All backups running to this new storage fail. In PCS logs you will see errors like:
2019-06-19T12:58:48:605+02:00 5624 E00000000: rq#484: v1req_get_short: failed to start connection: -4 (Misc network error)
2019-06-19T12:58:48:605+02:00 5624 W00000000: rq#484: communicate_get_file_info: failed to send the request: -4 (Misc network error)
2019-06-19T12:58:57:650+02:00 5624 W00000000: cl#5: failed to resolve the hostname 'old_hostname:44445': 11001
The agent does not renew storage address automatically and still looking for the old storage, that was already removed.
The issue has been fixed in Acronis Cyber Cloud 8.0, please update to the latest build.
As workaround, manually clear FesURI parameter in the registry as described in Acronis Storage and Acronis Storage Gateway: how to clear FES address from Agent's cache