After a power failure, ESX won't boot and stuck on nfs41client loaded successfully.
It's ESXi 6 Build 5050593 on a USB.
I tried to upgrade ESX to 6.7 U3 to no avail: Vibs on the host are conflicting with vib in metadata.
We had similar issue.
It does not stuck, it is so slow.
Do you have any RDM LUN presented to server?
If yes, you should change one flag perennially-reserved to true.
For now, you can disconnect all RDM LUNs from server, reboot and it should boot fast.
After that check KB: VMware Knowledge Base
If you don't use RDMs....I don't know
Its more likely a storage connectivity issues.
As Murali said press Alt+F12 and check the in memory logs to find out the cause for it to get stuck.
Keep us posted.
Had this same issue and the Alt-F12 to see logs explained why. The host in question was part of a previous cluster and had NFS mounts to ~20 volumes. On startup it was trying each one sequentially and after 60-90minutes it moved past the nfs41client message and finished booting.