Ok got it solved with all the responses here /s ;p
Just hope it will help someone else so sending an update.
If you have RH access you can follow this:
Run cert_date.sh script on your hosted_engine. It will show the expiry of certificates on your hosted_engine and the hypervisor host itself.
Based on that you can see what the appropriate way forward.
Run /root/singlehost.sh hypervisor-hostname
(had to run it with the -f option IIRC)
This fixed the VDSM certs (Host certificates) and some of the RHV-M certificates (it didn't for the certs in /etc/pki/ovirt-engine/certs/)
hosted-engine --set-maintenance --mode=global ## on the host
engine-setup --offline ## on the hosted_engine VM
Make sure to say Yes to the question to regenerate certs.
I still got an error during the engine-setup script about it not being set to Global Maintenance mode (which I certainly did).
/usr/share/ovirt-engine/dbscripts/engine-psql.sh -c "UPDATE vds_statistics SET ha_global_maintenance ='t'"
After this rerun the engine-setup --offline script.
Now disable the global maintenance mode again.
hosted-engine --set-maintenance --mode=none
Another one that might help: