I’m using the latest version of Zwift with a Tacx Vortex Smart running the latest firmware (3.1.13).
In Workout mode, Zwift doesn’t change the resistance as the target wattage change - the only way to keep on track is to either alter the cadence and/or change gear.
The Erg Mode box is ticked for the workout before starting.
It also didn’t work on the previous Vortex firmware version either (3.1.7).
Zwift does change the resistance for hills/descents when riding around on Richmond/Watopia.
I’ve also tested the Vortex with both Tacx TTS 4 and the Tacx Workout app, and they both successfully adjust the trainer resistance as the wattage changes, whilst I’m staying in the same gear and pedalling at the same cadence.
Is there a way to troubleshoot if this issue is specific to Zwift?