Recently, I upgraded my vCenter to 6.7 U3 and afterwards I wasn’t able to into my vCenter appliance via SSH and more surprisingly I wasn’t able to log into the VAMI.
Reboot of the vCenter Appliance
I was able to log into the VAMI
I went to Access > Edit > enable SSH
I was then able to putty into the vCenter Appliance
Took a while troubleshooting and looking through documentation and google. I finally got frustrated and rebooted the appliance to see if it would fix the issue and bingo. I hope this helps anyone else who runs into the same issue.