Check Windows Registry (run regedit.exe) and make sure ConfigPath points to the correct path to the location of webapimanager.ini.
HKEY_LOCAL_MACHINE/SOFTWARE/TODAY Systems, Inc./BuildProfessional Web-API/ConfigPath
The ConfigPath determines the location of webapimanager.ini which in turn provides the configurations for the Web-API Manager.
If ConfigPath is set correctly, will always place log messages in webapimanager.log.