How to make IncrediBuild work on a slow internet connection?

Question

C++ / C#

Hello.
There is a medium-sized project in C++. At the moment, it is assembled in a virtual machine on a poppy. A full build does not take very long, 7-8 minutes, but since there is an opportunity, I decided to study new tools.
On another continent across the ocean there is a powerful screw machine, the connection speed is in the region of one megabit.
Decided to try using IncrediBuild. I set everything up, the remote agent is visible in the coordinator, but when I try to do a Network Connectivity Test, it first shows that the agent is connected, then it goes blank for about 30 seconds and then "Failed to connect".
All ports are open, everything is fine with this. Sometimes the Network Connectivity Test gives a speed (receive performance) of the order of 1mbps, but the result is the same: Failed to connect.
When building, this agent is added as a helper, but does not compile any files. It starts compiling, but takes so long that all files are eventually compiled by the local agent.
Raised a virtual machine on a neighboring laptop, a wifi connection, the actual transfer rate is 150 megagits, put an agent there, Network Connectivity Test shows Status: Connected, 1.000 mbps and the correct actual transfer rate. At the same time, it marks the speed as Poor (since it does not reach the speed of the adapter in the virtual machine)
When building, this new agent does not help, it is not even added as a helper, all the work is done by the local agent.
Question. How to set up correct work with a remote agent and is 1 megabit speed really not enough for a comfortable parallel build?
Thank you.