Here is one for you, I have a advan 21cn BT openreach router, with 1gb synchronous connection, with a sfp output, this goes with a twin multimode fiber patch lead to a media converter, from the media converter with a cat5 lead into p3 wan on draytek. 3910, showing at the moment 400down and 650up.
Now if I put the fibre straight from the bt box into P1 sfp into draytek, with the same settings for wan as p3 port nothing...no connection, any idea?

The draytek 3910 is very buggy so I'm at all surprised it's not working.
Try loading system defaults and try setting up again

Oops wrong thread

From what I've found online, it looks like the ONT might be linked to your line's connectivity?

I mean, try setting the SFP to 1Gb or 10Gb port modes, but I think the connection might be linked to the ONT's MAC address or through some other means.

Could also be that media converter isn't compatible with the Draytek. I would have thought it would be able to negotiate the speed.
However the 3910 is a buggy piece of kit.

Did you ever get it working properly?