State of knowledge

December 2020. 

Observation

After updating ProCall Client to version 6.4.13, the connection to EWS (Exchange Web Services) no longer works.
When trying to configure the EWS mailbox via ProCall My Computer settings, the error message: "Microsoft.Identity.Client" or a dependency of it was not found.

Example screenshot: Error message in the ProCall workstation settings 

Solution

In ProCall client for Windows version from 6.4.14, this behavior does not occur anymore. Please update the ProCall client software to a version with version status at least 6.4.14.