Zwift under reporting watts

Hi, can anyone help please.
I have been using zwift for a while now and have just purchased a Tacx Vortex smart trainer.

I have set it up and calibrated it and paired it with Zwift.

My issue is the watts zwift is displaying is over 50% less then what I would usually record.

I am genuinely struggling to get the reading over 150watts. When I would typically ride for an hour at around 260-280 watts

I would generally aim to be around 3.2 w/kg during a ride and cant get above 1.6w/kg.

I have switched back to my “dumb trainer” to see if it’s an issue with my new Tacx trainer however this is also now showing really low watts per kg.

Is anyone else experiencing issues like this. It has only happened within the last 24 hours and prior to this has been spot on.

What did you use to confirm your past watts on a dumb trainer were accurate? Do you have a power meter on the bike? If so, why not use that with the new trainer too.