Power recognition

Hi. It’s almost certainly me, but I’ve been riding Zwift for about 3 months now and have a power watts range of about 140w to 220w for a ride depending in it being a social or pushing myself.
However, since Thursday my watts output has dropped to about 100w and my max if I push really really hard can get up to 150w for a minute or so.
I cant understand why this has happened as I’m now cycling at about 1.5w/kg instead of 2.5 to 3.
I ride a dumb turbo and rely on a speed and cadence sensor. I’ve changed the battery, but no difference.
Any ideas?

Did you accidentally pair it as a different model?

Thanks Ben, unfortunately not as checked that possibility