Here is the link to the Tool hub:

https://proconnect.intuit.com/community/system-responses/help/fix-common-problems-and-errors-with-th...

You state you uninstalled and reinstalled the SDK. But the Lacerte program itself has had a lot of updates, which might be your issue. The UI updates would affect the data files that the SDK are trying to work with.

Also, you mentioned replacing the dll, but did you manually reregister it?

And lastly, are they Running as Admin?