The issue is finally resolved!. For anyone who is facing the same, I will mention the workaround below and I hope you also get this problem resolved:
I just deleted the vCenter Server and Re-added it..... That's it!!
Can you believe this wow
Enabling / Disabling Provisioning of the vCenter also didn't work for me, so just go in your Horizon Console ->View Configurations -> Server.
Select your vCenter and click Remove
Then just re-add it again.
Thank you very much