Within the configuration file of CardExchange® Visitor is a commented out section as shown in green below:

Uncommenting this section will cause all database queries to be logged to the specified file. CardExchange® Visitor produces a lot of SQL queries so database logging is disabled by default, but if there are any issues you can enable logging to help identify the problem.

The default location for the configuration file of CardExchange® Visitor is below:
C:\Program Files (x86)\CardExchange Solutions\CardExchange Visitor\VisitorExchange.exe.config