I get the attached message when I try to load filament. It doesn’t matter which filament I try to use. I am using the A1 with AMS. I removed all the filament and reinserted it, I removed the tubes and re inserted them, I tried different filament, tried different files, unplugged the AMS a few times and reinserted them and a factory reset. I get the same message, no matter what I do.
Your filament sensor might be damaged or disconnected from the Toolhead Board.
Please check this article to verify if the ribbon cable of the sensor is properly connected.
If this is not a problem with the connector, usually replacing the filament sensor would solve the problem.