As described by JC-LAN, I had a lot of trouble with one particular "special" VMDK on a ESXi 6.5 system, which did not start after a reboot of the ESXi host.

The power-on failed with "File system specific implementation of LookupAndOpen[...] failed" - however in the end it just gave me the overall error that it failed to start the machine. As it turned out, the VMDK was corrupted.

1.) Enable SSH on the ESXi host with the corrupted VMDK - and login

2.) Check the main VMDK (not with the name -s####.vmdk, the main file!) with

vmkfstools -x check /absolute/path/vm.vmdk

3.) It will probably report that the fail is defective. Repair with

vmkfstools -x repair /absolute/path/vm.vmdk

4.) Now you can try to start the VM again, helped me already 3 times 🙂

Taken from: https://jc-lan.tk/2017/02/01/esxi-6-5-host-crash-then-guest-fails-to-power-on/