Have tried replacing the sy_forms.... file in MAS_System.
Tried uninstalling Sage 100 client and e-filing software.
Any other ideas?
This is Sage 100 2019 Standard PU2.
Did you look at KB ID: 78858?
I finally got this working yesterday by adding those 3 sites to the Trusted Sites in Internet Options
Of course we had already exhausted KB ID: 87888 & KB ID: 25334
*Community Hub is the new name for Sage City