If Meterpreter Gets Stuck on Sending Stage, Is Exploit Not Compatible with Victim System?

I am using a veil evasion exploit that is embedded inside a Excel document, and is not detected by AV. I have tested it myself on different WAN computers(windows only) and it has worked perfectly, but now I tried to execute on on another computer(the victim a friend, knowingly doing it) but I asked him not to tell me if he has a MAC or Windows Comptuer. If it worked on windows before with WAN computers, can I assume since it is stuck on the sending stage that the exploit is not compatible and so he must be using a Apple Mac computer? As it has worked on windows 10, 7, and xp so the only reason I can see is that he is using MAC, since it has been tested on WAN with different windows and different excel versions.

Thanks