Problem
When MCAS is setup in Office 365 environment, users are unable to open both Workflow and Form because now the URL has changed with additional mcas.ms
Solution
Nintex currently does not provide any accreditation or official support for Microsoft Cloud App Security (MCAS).
If MCAS is enabled then kindly disable MCAS as Nintex is not compatible with MCAS.
If you would like to see this feature in Nintex please vote on the following feature request: https://ideas.nintex.com/ideas/IDEA-I-1381