Context:

EveryonePrint MobilePrint 4.3 Email print setup for O365 hosted Exchange with "Modern Authentication" as per section "18.8 Configure Email Print with Microsoft Oauth2 Modern Authentication" of the Install Guide

Issue:

When doing the test the following error is received: 

Incoming mail test failed. Your settings do not appear to be correct.
Error details: AADSTS7000218: The request body must contain the following parameter: 'client_assertion' or 'client_secret'. Trace ID: 014652a0-220e-4f9e-a98d-01e45d95fc00 Correlation ID: cff72ef0-3c3c-4ad9-bff0-26329426229b Timestamp: 2021-03-24 15:51:12Z AADSTS7000218: The request body must contain the following parameter: 'client_assertion' or 'client_secret'. Trace ID: 014652a0-220e-4f9e-a98d-01e45d95fc00 Correlation ID: cff72ef0-3c3c-4ad9-bff0-26329426229b Timestamp: 2021-03-24 15:51:12Z

Resolution:

Verify step 9 in the setup