Acronis True Image 2021: Downloading protection updates hangs if port 8099 is in use

Symptoms

Downloading protection upgrades hangs at the beginning with message Calculating time remaining and makes no progress for several hours or more.

Cause

One of the possible causes is that port 8099 is already in use and Acronis process GRPM-mini cannot use it.

To verify, check the logs for GRPM-mini process:

Windows: C:\ProgramData\Acronis\Agent\var\log\generic-resource-policy-manager