Premiere source monitor doesn't play in a external monitor

Hi

I have an ultrastudio 4k. Premiere's timelime is in HD and the source material is in 4K. I can playback correctly the program monitor in the external monitor (SDI) but when I check in the clips n the source monitor the signal is not output to the external monitor.

I have reset premiere's preferences and I doesn't work.

Do you know how can I fix it?

Regards in advance

Do you have a 4K monitor? If you make the sequence 4k instead of HD does it still play from the program monitor?

I also have a similar problem in that my material is 4K 50fps Braw and my Studio 4K will not show this as it only goes to 30fps. Most of my sequences are HD 50 and these work fine but any native material in the source monitor will not play to the external device.