71A3 fault in ABB DCS880 drive indicates Mechanical brake not opened. This means the acknowledge signal at the DI for the mechanical brake opened (applied) stage is missing.

1. Check the mechanical brake itself.
2. Check the mechanical brake cable connections.
3. Check the mechanical brake settings in group 44 Mechanical brake control.
4. Check that the acknowledgement signal, if used, matches actual status of brake.
5. Check the used digital inputs and outputs (groups 10 and 11).