I built a simple keyboard using Keyman Developer on Windows 10. I installed the keyboard on a MacOS system.
The OSK on Windows displays all the layers correctly.
On MacOS, the main layer and Shift layer display correctly, but the Alt and Alt+Shift layers are blank. No characters are displayed in these layers.
But, I am able to type the characters correctly! I just can’t see them on the OSK.
I also installed one of the keyboards from the Keyman website and that keyboard has all the layers displayed correctly (including Alt and Alt+Shift) on MacOS, so I don’t think it’s a settings issue.
Has anyone seen this problem before?