Our developer read your license file, it looks you have a WPF eval is expired, it looks maybe that's the reason of your problem. But in our test that won't effect the result because our logic handle this scenario.
So could you please test the simple sample I built in your machine?
As below is a simple sample which for reproduce your scenario, I build a Winform project, then modify it to a dll, and after that I build a new Winform project named UI.exe which reference it and call it.
Map Suite Desktop for WinForms App1.zip (117.2 KB)
Before test, please deactive your product(winforms edition) in your product center. And copy one of the license file between the 201901 license file and 201811 license file into Map Suite Desktop for WinForms App1\Form1\bin\Debug folder. And you can try to run the project without the license file, it will throw exception.
In my machine, the two license file works the same.
If you can reproduce this issue based on the test project please let me know, we will find some other solution for you.
If you found anything is missed in test sample could you please modify it and sent it back? So we can double check where is the problem.