It's worrying how often their big updates break things, my older PC originally on W7 invariably loses sound and needs driver roll back.
The newer one no longer has any means to start up their own defender even though it's in program files and I re-installed it in the registry, it was completely missing.
I have full malwarebytes doing a similar job once I realised.
That happened to it about a year ago too - I eventually 'fixed it' by full repair install which deleted more than I expected so not doing that again in a hurry