If you are blocking Claims Authentication in your Microsoft 365 Tenant, you cannot add SharePoint Sites in to Adobe, no login prompting occurs.

Reproduction steps:
1. In SharePoint admin center > Policies > Access control > Apps that don't use modern authentication, set to 'Block'
2. Try to add a SharePoint Site to Adobe

Environment: Windows 10

Expected result: Successfully add SharePoint Site to Adobe

Observed result: No login prompting or errors occur, dialog simply re-opens and does not add the SharePoint Site

It should be noted other PDF applications such as Foxit and Bluebeam Revu both support Modern Authentication currently, so unfortunately this may mean we have to move away from the Adobe Suite to other software suites for security reasons in the near future.