Zoom Unstable Connection and No Screen Sharing on 250mb connection

[Fuzed]

As in the title Zoom is unstable and does not allow me to share (just times out at other end) my screen on my NBN Fibre 250mb connection. However when I am in failover mode on my 4G sim mobile connection at 30mb it works fine. 

I have tried several different solutions but not really knowing what I am doing. Any help much appreciated.

[bstrelko]

It's possible (likely) that there are restrictions downstream on the 250mbps fibre connection at the firewall level. If you have this info, can you tell us a little bit more about the setup for both connections?

example:

-Wired connection into [Manufacturerer][Model] Switch

---Switch settings - firewall, port blocking, etc
-Switch connects to [Manufacturer][Model]modem from [ISP]

---ISP settings/restrictions

This will help us to identify where you may be running into issues. My initial thoughts are that the firewall somewhere downstream on the fibre connection is preventing specific traffic.

You never have issues with camera video transmission and receipt, correct?

[Fuzed]

Thanks bstrelko.

I am on a wired GB ethernet connection to a UDM PRO switch. Both the NBN 250mb and 4G Failover are connected to the switch with identical settings apart from IPV6 is disabled on the 4G (no idea why).

I don't think it can be a firewall as the connection does go through just incredibly lagged on the NBN - yet instantaneous on the 4G.