Hi,
Install lastest version of SAP Lumira 1.29.3
Open run (Win+R) and type %APPDATA%, you will be taken to the Roaming profile folder. Navigate to the parent folder. You will find the local profile folder, inside that navigate to SAP -> Lumira -> Database. Delete all the contents of the folder.
Once after installing extensions check in .sapvi folder and see weather you can see the installed extension(s).
On opening SAP Lumira, check task manager, check its performance of SAP Lumira.
If Usage and memory is high rise ticket to SAP Lumira support team.