If you are in the process of upgrading to NSX 6.2.3 and hit the above issue have a look at the following KB.
This issue occurs when serverSsl or clientSsl is configured in load balancer, but ciphers value is set as NULL in the previous version.
VMware NSX for vSphere 6.2.3 introduced approved ciphers list in NSX Manager and does not allow the ciphers to be NULL for serverSsland clientSsl in load balancer.
Note: Default ciphers value is NULL in NSX 6.2.x.
Since the ciphers value defaults to NULL in the earlier version, if this is not set, NSX Manager 6.2.3 considers this ciphers value as invalid hence the reason why this issue occurs.
There is a workaround in the above KB which involves making a POST API call to set ciphers value from NULL to Default.