After `telnet`ing to a device, can not see the device prompt

I have a virtual router on a server and I have assigned a port no – 20171 to a serial port

And I connect to this device using the cmd –
telnet 10.X.Y.Z 20171

And after that I see something like this –

Trying 10.X.Y.Z...
Connected to 10.X.Y.Z.
Escape character is '^]'.

indicating that telnet session is successfully established.

But after that I don’t see any console prints from the router. Neither the Router prompt.
What could be the issue?

Note: If I change the serial port number to another port say 20172, then I see some logs.

I’m using bash running on RHEL as a telnet client