Teams Video Not working

Using the MS Teams desktop app, if I accept a video call from a client they cannot see me and I just get a frozen image of them.  we can hear each other. If I send the invite and they accept, this problem does not occur i.e. it works fine.  So I can host meetings but not join them with video.  This does not happen if I use the web version.  So I have had to uninstall the app (tried reinstalling - same issue) so temporarily my problem is solved as I can use the web version, but as I have never had a problem with the desktop app until today I am at a loss. Video works fine using Zoom. (and with Teams, as long as I am hosting).

any ideas?