When a scenario begins its arming sequence it checks the current hardware configuration selection (see FAQ10273 to learn how to manually check the current configuration). If a multibox configuration is in use it will check the Master unit's timer output settings. If those settings do not include:-
then it will inform the user of this fact through the warning message = Warning: TIOP setting incompatible with External Triggering
This warning can be ignored if the user has chosen to use the DISABLED trigger mode (this is the default mode). But if the user has chosen to use the IMMEDIATE or DELAYED trigger modes then they should check the current timer output settings on their master unit and update them accordingly.
To learn more about timer output settings and how to change them please refer to article SOL10178
To learn more about trigger modes and to change them please refer to article SOL10180