I have a tacx flow that I am trying ot calibrate.
It keeps telling me too loose and to tighten but I cannot tighten any tighter
DC Rainmaker has some hints re Flow calibration in his review.
What size wheels & tires?
Which frame mounting holes (upper or lower) are you using?
How are you calibrating (TACX Utility App, TACX Training App or on a device eg Garmin etc?
My related experience below but might not be your problem ?
It only takes a few minutes to change so I would try with the resistance unit mounted in the lower holes.
I could never get the Utility App to calibrate at all but the Training App and Garmin Indoor Trainer calibrations worked fine.
Otherwise Garmin Support?
Good Luck, hope it works out ok