So simple but so hard.
Having a bad cold I'v been home for a few days. Finally I could bend down without my head exploding so I could replace a harddrive in my ceph system.
I took everything off line, installed the new drive and did all the right things,
but afterwards it didnt come up.
It didn't make sense so I googled for hours while my fever were getting stronger without finding the answer.
So I gave up and reverted my changes and plugged in the old harddrive...
It still didn't work... a bit of panic. I mean... its all my files!
After a lot of sweating (no caused by fever) I realised I moved two ceph-mon processes a few weeks ago but I never rebooted the system afterwards, to fix it all I had to do:
systemctl enable ceph-mon
on two machines.

Summary: make sure things work after reboot and don't do challaging stuff while your brain is all scrambled.