As soon as I posted this I found this OP which resolves the issue, so posting this here for anyone else who comes across the same.
https://forum.falcon-bms.com/topic/18019/tried-opentrack-now-lost-ability-to-mouse-look-in-cockpit/7
As mentioned in the above post, renaming the {opentrack install dir}\modules\NPClient64.dll fixed it for my scenario. Can rename back once camera is sorted.