Firstly a cou tip I got from NPE.
Currently if you want to have cadence running shown on Zwift via Ant+, you can, but only if you ALSO connect the Runn to the Zwift Companion app via BT at the same time.
2nd tip. Too many stickers or marks on the treadmill belt can be bad idea, as they can blur at high speed and cause issues. Keep your stickers at least 2ft apart.
Finally, my rant and dev request. I understand during cycling on Zwift, power is king, if you generate some, your Avatar moves forward. Cadence is only used for leg movement. However, using the Runn on the treadmill, your Avatar goes the speed the Runn is measuring, EVEN if you still standing on the edge of the treadmill allowing it to speed up, or perhaps after a hard interval. Surely Cadence should play a much larger part of the calculation in Zwift for running, in that there should at least be some binary check that steps are occurring as proof that effort is being expended, not just Zwift measuring the treadmill speed via the Runn?