Are you accessing the website from a phone tethered to the PC, using it's connection? If so, you've ruled out IP issues.
We'll start simple. Tell us the operating system and web browser (as well as add-ons) you're using on one machine... say, the PC.
If you are just using Internet Explorer, it's possible you've downloaded something that blocks access. You can restore IE to original settings by going to Tools > Internet Options > Advanced > Restore Settings.
Additionally, you could try a browser like Mozilla Firefox or Google Chrome to see if you have better results with them.
