Extensions need permission to run in private windows in private browsing mode.

Thank you. But! One already had permision and was/is not shown; and the other two were given permission - but problem not solved. I use "never remember history" for privacy - my win 10 FF addons work perfectly with the same setting. When I started populating Win 11 there was at one stage a major update - does 2H22 ring a bell? I wasn't paying full attention in that it may have been the cause since FF and addons were pretty well the first application to be installed - and IDM, at least, was working at some stage - I just can't remember whether before or after the update.

Extensions will not appear in the toolbar by default, you need to pin them from the jigsaw puzzle button.