Welcome. Its my first experience with Zwift. I’m using Star Track Spinning Pro + Garmin speed/cadence sensor and Bontrager pulse sensor. I’m unable to exceed over 400W. It does not matter if cadence is 120 or 150, max Power is 400W. Why is that?
Rgds
Remi
Is that a spinning bike?
Zwift don’t have a power curve for spinning bikes, they can’t calculate the power curve because they can’t know on what resistance setting you are at.
Averaging 330w at 117bpm is just not normal.
Yes, Thats spinning bike. I thought that it is some kind of algorithm which calculates Power basing on cadence/speed as it displays the power. But why till 400W only 
I know that the best option is to have equipment with resistance sensor, but at the moment I only have that set
400 w is the capped limit for un supported bikes without power meters.
Because zwift does not know anything about the resistance settings of the spin bike, its making a wild guess of your power based on the speed sensor.
If you can actually produce over 400 w for an hour that makes you a top tier cyclist, Zwift is just assuming your not a pro and capping your power.
See: