Siri on MacBook Pro

I've always used Siri on my 2019 MacBook Pro - until it recently stopped working. I can open it, but instead of the little speech graphic when I talk, it simply shows the Siri box - with a tiny question mark. I haven't managed to find any info on Google as to why this might be happening. I've gone into setting, Mic is working etc - just nothing, whether manually opened - or using "hey Siri".... Help!