I have exactly the same problem with a new Elite Qubo Digital Smart B+.
Seeing as you are using the app Im guessing your connecting via bluetooth as well. Are you able to pair yours by the “power” sensor?
Part of what I think is causing the issue for me, is the qubo doesnt appear in the pairing under the “power”" selection list (even though its a smart trainer), however the device does show up under the “classic trainer” device listing.
Soon as i spin the pedals the power is maxed out, same as you describe above.
Depending on what classic trainer i choose you end up with:
Generic = limit of 400w / any other elite trainer = 1200w.