When loading Microsoft Office products, DLP MIP integration should prompt a user for MIP credentials so that DLP can inspect sensitivity labels and decrypt MIP encrypted documents, but no credential prompt occurs.
15.8 introduced a new executable auth.exe that exists within the Endpoint Agent installation directory. As this is an executable not previously included with the product, it may be missing from antivirus exclusions.
Please ensure that auth.exe is included in the necessary A/V exclusions per Technical Article 160045