Cubase 5 is not playing from an external MTC signal


I am trying to trigger Cubase 5 from an audio timecode signal via MTC.

I have striped track 8 on my analogue tape which is then fed into XR300 smpte box via an audio cable. The smpte box then generates MTC and outputs it via a 5 pin din midi cable into my Focusrite Clarett 8Pre. I can see the midi light flasing on the Clarett when the tape is played so I know it’s getting that far.

I have downloaded MIDI-OX and can see the MTC being received.

I have set the Timecode Source in Project Synchronization Setup to MIDI Timecode and set the MIDI Timecode Source to Focusrite Clarret USB. I have set the Frame Rate to 25 fps in the Project Setup menu to match the smpte box’s frame rate. And lastly I have set Use External Sync in the Transport menu.

When I press play on the tape machine I can see the XR300 reading he timecode but Cubase does not start. I have tested the exact same setup with Abbleton Live and it works, so I’m guessing there’s some setting in Cubase that I’m missing.

Any help would be greatefully received as I’ve spent hours on this with every combination of setting.