Flowmaster Digi FM controller won't turn off and keeps going up to 99 have tried to recalibrate but un successful,
What model controller is it? V11 etc.
I would remove the fuse or disconnect the power to the controller on the battery and leave it for a few minutes. Then reconnect. This might help to reset the controller.
Most failures on the older V11 controllers were reverse polarity when connecting the battery up and water ingression.
The latest controller V16 controller is protected against reverse polarity.
Otherwise your best bet is to contact Ian Sheppard at Spring Europe.
ian.sheppard@springltd.co