I was able to resolve this by opening the required ports in our firewall. I happened to be connected to vCenter via VPN. Our VPN has many more ports blocked. I used the TCP and UDP Ports for the vSphere Client guide to ensure the proper ports were opened. Essentially, you'll need TCP and UDP 443, 902 and 903 opened to your vSphere host, not your vCenter server (if you have one).
Thanks to Alim786 for the answer in another thread!
