Unfortunately, vRA (any version) does not support Enterprise PKS (anything past 1.2 1.3 [vRA 7.6]). What causes this to break is generally using OIDC authentication. I have been told by the powers that be that they will not fix this in vRA and the only product which officially supports it is vRA Cloud (formerly Cloud Automation Services) and the forthcoming vRA 8.0.
I see. Well I appreciate your insight once again!