When I try to print a preview, I get an error (in Swedish) "Cannot find path" followed by "Cannot find Winprint Viewer's Window". This is in the call to WP_NewDocument in Winprint2.pkg, line 335.
After that I get the same two errors, from the call to WP_PreviewDocument on line 238.
After this, I get (in Swedish) "Error using Winprint. Could not show preview !"

The same code works with 19.0, and I also tried copying Winprint.dll from 19.0 and this made the error go again.
This is 20.1 Release, 32 bit.