Mate desktop no longer give main menu icon, which gives choices like internet,sytem=>konsole etc

I am using thinlinc client (v1.20), to connect linux box(ubuntu 24 container) running ThinLinc server software. I am using Mate desktop to login. It was working before, but suddenly, I don’t see main icon (button on top left). I tried connecting/disconnecting; ending previous sessions etc.
Any idea? Thanks for help.

-also do you know, what directories/files ThinLinc creates for housekeeping on laptop and Linux machine. I need to know, if by removing those directories/files may help.