The message APTDB EXP appears even though the database on the microSD card is up to date

1. Position source sends incorrect data:

The position source for the ACD, which is used, among other things, to check the current date and thus the validity of the database, provides an incorrect date during startup.

The date is checked immediately after the ACD is switched on. However, some position sources sometimes send an incorrect date during their own startup process. 

Solution: You can remedy this problem by starting up the position source first and then switching on the ACD-57.

2. Multiple files on the microSD card:

There is still an old file on the microSD card.

Solution: Please remove all files on the microSD card except for the current valid database file.