Guitar Plug-ins - not able to monitor when playing / recording. Only on playback.

Hi.

LogicPro 10.8 and 11. Ventura. ZOOM Tac-2 Interface. Monitoring turned on. Core audio on. Audio settings correct. Until recently I could monitor my guitar tracks, including plug-ins. (Sometimes the plug-ins could only be monitored when recording ?) Currently all software and assigned plug-ins can be monitored at all times. Guitar tracks can not. I can hear the guitar through the interface when Logic is not running. I can see the Logic track level meter responding to the guitar input and it records perfectly. But I can no longer monitor this guitar 'on the fly', which makes it impossible to correctly add effects while recording during project playback.

Help would be fantastic please.