Hi Joddle,
If no device can access the site I wounder if this is IP Address related.
Ask your colleagues to firstly find their IP Address.
Simply Google "what is my ip address" - it will come up on screen.
Make a note of this.
The easiest way to change the IP Address is to turn their router off for half an hour.
Then switch back on.
Check to see if IP Address has changed.
If not - switch router off over night.
Try again in the morning.
Check that the IP Address is different. [ probably only the last 2 numbers will change ]
Most IP Addresses are dynamic - in other words if you are not using it the ISP will re-allocate your old one.
When you connect again you get allocated a new one.
Let me know how this goes.