In the Windows Event Viewer log you can see the following error message:
FlexiBr: Processing Server restart: An error occurred while creating Application Server session: Not enough rights on Application Server.
It means that the user account under which the Processing Server service is started does not have appropriate permissions on the Application Server. By default the Processing Server service is started on the computer under the NetworkService user account.
On the Application Server you need to assign the Processing Server role to the user under which the Processing Server account is running. Find more information on the subject in the article of the FlexiCapture 12 System Administrator's Guide.