Telnet

I'm stumped, have you setup telnet to go via another port or something.
port scanners can find it hard to pick up on a non standard port and can be very time consuming, it is possible you set it up on another port and your router is blocking that port which could be a reason a port scanning isn't picking it up and why you can't access it.

I can't remember how you setup telnet on windows, but if you configures it to another port you add it after the ip e.g.
telnet 123.123.123.123:23