If Blackbaud Hosts your NetCommunity database, Click Chat with Support and reference this article.

If your NetCommunity database is not hosted by Blackbaud, work with your IT department or database administrator to perform the following steps on the NetCommunity Web Server:
  1. Open BBAppFx on the Blackbaud NetCommunity Web Server - typically in a location as follows: 'C:\Program Files\Blackbaud\bbappfx\MSBuild\bbAppFx.Config.exe'.
  2. Select AddApplication User
  3. Confirm the corect Server name and Database name for your environment are listed.
  4. Set IsSysAdmin to True.
  5. Input nt authority\network service as the user.
  6. Click Go