Unlike previous 6.3.x releases, 6.3.5 has some new upgrade minimum version compatibility requirements. This is not only true from a vSphere perspective, but also for the version of NSX 6.2.x you are running. If you are running an older 6.2.0, 6.2.1 or 6.2.2 release of NSX, you’ll need to upgrade to at least 6.2.4 before taking the big step up to 6.3.5. VMware has just updated the NSX Upgrade Matrix to reflect this requirement:
I expect that VMware will update the 6.3.5 release notes and release a new KB article very shortly. I’ll provide some more detail when that is out. In the meantime, please be sure to heed the version requirements or you will most likely run into problems.
Thankfully there aren’t too many customers still running these old releases of 6.2.x, but if you have already attempted the upgrade and hit problems, you’ll need to roll back. If you took a cold-snapshot of the manager or a clone, you can roll back that way. Otherwise, you’ll need to deploy the original 6.2.x OVA again and restore your FTP backup.
** Edit 11/29/2017: VMware has just updated the NSX 6.3.5 release notes to include mention of the minimum version requirements. The following statement was added:
Important: If you are upgrading NSX 6.2.0, 6.2.1, or 6.2.2 to NSX 6.3.5, you must complete a workaround before starting the upgrade. See VMware Knowledge Base article 000051624 for details.
VMware calls it a “workaround” but it’s basically just upgrading to an interim version before going to 6.3.5. In KB 000051624, VMware recommends going to 6.2.9 as that workflow has been tested. I.e. upgrading from 6.2.0 to 6.2.9, and then to 6.3.5. On a positive note, you only need to upgrade your NSX Manager to 6.2.9, no other components need to be upgraded before proceeding on to 6.3.5.
If you attempt an upgrade from 6.2.2 or older releases, my understanding is that the upgrade will appear to be completed successfully, but your configuration will be missing. VMware calls out the remediation steps of rolling back to the previous version should you run into this issue.