Udenjoe is right. You need to activate the transport control on your TR8, as well as setting the OT to allow receiving transport messages.
If feeling for going more flexible, given that the settings are available, you can actually have both the ‘clockmaster’ and ‘clockslave’ with their respective transport send & receive active, given that the MIDI connection between them is bidirectional in any sense. Then you can press play/pause/stop on any of the units and both will react. OT can have both send/receive clock activated at the same time, but I don´t know if your TR8 allows both send/receive clock at the same time? So syncing them might be ‘one-way’ only…