Teams developed a crash on startup.
Saw various messages such as an Azure AD sign in failure whch s strange as we don't use Azure AD for local domain authenticaton.
We do use a centrally provided Azure sign in for Office 365 applicatons though.
Finally tracked down this article on the excellent Petri site:
Gave the option to delete the Teams cache at %AppData%\Microsoft\Teams and this fixed the issue straight away.
The teams client did initially come up wth my AD logon, so perhaps it was trying to authenticate my domain logon against Azure?