OpenVPN + RDP = working on WIFI, but not on cell data LTE (Fido/Rogers)

Question

Hello,

I recently got configured to access company computer using OpenVPN and Microsoft RDP
I have set this up on my macOS imac, and it works no issues.
I have set this up on my iphone, and it works only when on WIFI.
If I turn off WIFI, and use my cellular provider (Fido/Rogers) LTE data plan, I am able to connect to OpenVPN (internet access works, and I can ping the workstatation PC I am trying to contact), but cannot connect using the ios RDP app.

My IT guys says its probably something the cellular LTE data is blocking on the VPN side, but the VPN seems to be working as I can ping the computer and can access the internet. I'm wondering if its specific ports that the RDP uses, that is being blocked.

I do not see any specific ports on the settings of the RDP app, does anyone have any ideas or suggestions?
Thanks in advance,
Mike

Answer 1

Small update:

I tried tethering my imac to my iphone, therefore using fido LTE data

openvpn + RDP = works!

So why would there be a difference if my imac is using fido lte data vs my iphone ?

Iphone on WIFI : openVPN + RDP = success

iphone on FIDO LTE : openVPN + RDP = no success

imac on WIFI : openVPN + RDP = success

imac on FIDO LTE (via tethering) : openVPN + RDP = success