Software boutique coat hanger disappears

Hi, I've just reinstalled Ubuntu Mate on my Raspberry Pi 4 (4Gb). Everything appears to be working, but.....when I launch the Software Boutique, the icon appears on my toolbar. When I click on it....nothing.....then the icon disappears.
Any suggestions?

Which version of Ubuntu Mate? I don't know if this is relevant, but I've only tried UM 20.04 so far.
For me the software boutique loads with no problems.

Working fine this morning. I moved the Pi to the left hand side of my desk. Better Wi-Fi signal there.