This from FSACARS web site.

[Wayne Pierce]

A couple of new pilots are not able to use FSACARS as it is not finding the FSACARS.mdb file. It is located in the FSACARS folder in the self installed directory. Looking at the FSACARS site it has this posted for new users;
1. Verify you have FSUIPC or FSUIPC 7 (MFS2020), or XPUIPC (X-Plane 11)
2. Verify you have .NET 4.5 or later
3. Some users report the need to Run as Administrator: fsacars.exe and fsacarsUpdater.exe
4. Antivirus softare may need to be temporarily disabled, and/or set to ignore fsacars
5. Web blocking software (eg., Trend Micro) users must add the domain to their exception list.
6. Currently not compatible with Mac or Linux

If you continue to have problems check this forum on our Web Site; viewtopic.php?t=15538

Thanks, WLP