[Lazarus] Application GUI does not appear

[Koenraad Lelong]

Hi,
It's been a while since I did some development with Lazarus.
Now I wanted to update an application I wrote some years ago. At that 
time the application was written and compiled on and for Linux.
Now I want that application to run on Windows 11 64bit.
I installed the latest Lazarus (2.2.4 64bit) on a Windows 11 machine and 
copied my sources to that machine.
After some struggling with a missing library (libmysql.dll) I managed to 
run the original application. But I could not see the GUI.
Then I discovered I could not modify the forms, I simply can't see them. 
Pressing F12 does nothing but greying out the caption of the editor.
I can see the form of the datamodule though.
I used the "Check LFM-file in editor"-tool and that checks OK for the 
GUI-forms.
I added an msgDialog in the on-show routine of the main form and that 
does show. But when I click that away, nothing shows anymore, just the 
icon in the task-bar.

I created a minimal application and that does work fine.

Any Ideas what is happening ?

Thanks,
Koenraad