Second time I try to post this I had to rewrite everything as the bug report wasn't visible.
I use a PC Win 10 64 bits home, 128Go Ram, RTX3080Ti, i9 CPU and latest version 11.1.0 Pro of Keyshot
Follow thèse steps:
1. create a new project
2. create a plane
3. doble click and make the material Area light
4. observe how the Area light is displayed in both main view and geometry view
5. now change the light to Spotlight
6. light disappears in both main and geometry view
6. as a workaround you can do this, copy the material from this plane and paste it to the same plane again
7. now the light is visible again.