Pro 7900: No ink reaching print head

[Vogelkop]

I need advice on this:

After cleaning and re-installing printhead in Pro 7900 it does no longer have ink reaching the head.
I have done a few cleaning circles and also a few power cleanings.

After inserting a new maintenance tank I realize that not a single drop of ink is coming through.

The prints are blank. The tubes seems to be full of ink (I think!).

I assume that the printer is missing pressure, but I do not know what to do next.

Any advice on how to troubleshoot this?

I do have another 7900 standing next to this. I managed to take out the print head and reinserting it without any air leaks.

I could swap the print heads but I would like a better solution..

Thanks,
Ronald