problem during reinstalling em client software

During first opening of software I got message that I have to degrade the software.
I have tried to uninstall en make a new install, but some how old data is left on the computer 
Deleted the emclient folder in AppData but problem remains
FYI : I used em client until 2016.

The default folder for the database is at C:\Users_yourusername_\AppData\Roaming\eM Client, but it is possible that you had it elsewhere. 

Maybe search your computer for a unique file that is in the folder like snippets.dat