If your mac is at home, try connecting it directly to your modem and reboot your mac.
Is that v.0.8.7.7? I have it running from my 10.12.3 as well with no issues. Is it always stuck at a particular block?
Try running it from terminal with ./zcoin-qt -reindex and see if it works.
That was before, now i have the 8.7.7 and still having the same problem. I can't run that command in the terminal, no such file or directory it says.