In order for certain inter-application integration to take place such as filling a form or manipulating a Word document, Probate Plus needs to be able to connect to the application in question.
When any application is installed to Windows it has the option of advertising services that it's capable of offering to other applications and does so by setting various "keys" in the Windows registry.
If these keys are missing or damaged for some reason (sometimes a failed application update or even a Windows update can trigger this), then Probate Plus may report that it was unable to detect the application in question or an error such as "interface not supported".
We always recommend carrying out a "repair install" of the application that Probate Plus is trying to connect to. In most cases a repair install tells the application to recreate any Windows registry entries that may be missing or incorrect. After this has completed, retry your task in Probate Plus and see if it can successfully connect to the application in question.
Here's an example of how to locate the "Repair" option for Oyez Legal Forms under Windows 10 "Apps and features".
It's perfectly possible for an application to be able to be manually opened but not have its Windows registry keys correctly set. In this case you may be able to directly interact with the UI of the application but Probate Plus is unable to connect internally as the mechanism isn't correctly configured.