External Timecode into UE

Hello
I’m really new to UE and I’m having a problem with getting UE to accept timecode.

I’m using a C300 MKIII which has SDI TC output.
The signal path is:

C300 Freerun Timcode- SDI to Blackmagic Ultrastudio 3G - Thunderbolt to Laptop - Media Bundle

The FPS and format settings are matching and timecode display has the green icon to signal that it’s ‘seeing it’ but the camera’s TC is not matching the UE TC.

Am I missing something?
Do I need Genlock too?

We have a BMD Sync Generator and Atem mini at work if those are useful.

Any help would be greatly appreciated!

Tom