Support for vmPRO ended December of 2017, the last code release for it was 3.3 which was released May 2015, so there are many things vmPRO will not work with. Also if the ESX that vmPRO is installed on is 6.5 or higher, vmPRO will not work.
Thank you for the update, our vCenter is still on 6.0, so recently as per security they disabled TLSv1.0 protocol under vCenter, so now only TLSv1.1 and TLSv1.2 are enabled under it, so checking if our vmPRO master appliance will able to connect via TLSv1.1 or TLSv1.2 to vCenter or not , as backups started failing once TLSv1.0 is disabled on vCenter