License not working

A user just purchased a license and when he enters it into our product it comes back as invalid. The same license key works fine for me (he's using windows, I'm using mac).

Is there any way to know if he is successfully contacting the LimeLM server?

What's the error code returned? At what point is it failing? That is, is the key not being accepted by the CheckAndSavePKey() function, or is it failing when he's activating?

Also, tell him to try copy/pasting the key instead of typing it. Sometimes users misread/mistype letters and thus they get an error.

Thanks. I don't have access to it but now my guess is he is on a school network that blocks access to the LimeLM server. Told him to take the computer home, try there and report back.