Acronis True Image 2021 (Mac): "You've exceeded the maximum number of activations for this serial number"

Symptoms

You receive the following message:

You've exceeded the maximum number of activations for this serial number

and/or

Too many activations

Cause

You exceed the limit of available activations. For example, you have an Acronis True Image 2021 1 computer license and attempt to install Acronis True Image on more than 1 machine.

Other possible causes: