Welcome to Communities and vSAN.
"All my vSAN pre-checks are validated however I cant pass the VM creation test."
Have you added Disk-Groups? Cluster > Manage > vSAN > Disk Management
Are they in CMMDS/VSI? Cluster > Monitor > vSAN > Health >
All nodes are out of Maintenance Mode? (note it is possible to be out of vSphere MM but in vSAN MM - validate via CLI with #esxcli vsan cluster get # cmmds-tool find -t NODE_DECOM_STATE)
What is the error message given for failure of Objects? If it is something like 'require 3 Fault Domains for component placement but found 0' then either cluster isn't formed, is partitioned, nodes are in MM or there is no usable space in some/all Fault Domains (nodes here).
Thanks for the reply, to answer your questions:
Health checks are all OK -
Disk groups are added, and the vSAN volume has capacity.
I have rebooted all hosts twice now so MM isn't an issue. (found the KB on this one)
It appears just read only - very strange
Rebooting a host won't take it out of MM (vSAN or vSphere MM), even if you do it twice - please share the output of this run on any host in the cluster via SSH:
# cmmds-tool find -t NODE_DECOM_STATE
# esxcli vsan cluster get
# df -h
If for whatever reason you don't want to post the output here online (not that UUIDs are of much use to anyone nefarious anyway! but domain/DNS names maybe) you can PM me the output.
Screenshot/copy of the error message in Proactive VM creation test may help here also.