Power increases but speed stays the same (on the flat)

I had my first ride on Zwift this morning. I was riding on the flat course. Using a Wahoo Kickr.

When I was passed by a rider I tried to jump on his wheel. I sped up and the power in Zwift increased as expected, by approximately 25%. Power the speed remained the same (I was going around 32km/h).

This was on part of the course where the gradient was 0% before and after I increased Watts. Is there anyway to fix this, ways to test why this is happening?

I have just done the update and having this similar issue. It feels like on flats i’m going up hill now since the update.

Wahoo kicker too

Wondering if I need to update the kicker? I send in a ticket as well