Some of my End-Users are Unable to Access Form

A couple of my end-users have told me they have been unable to access my form, getting this message: ‘Form is unavailable at this point’. It works fine when I open it. Please advise. Thank you.

From what I gather so far it seems that you are saying some of your end-users are unable to access your form on their end when they attempt to use it, correct?

I've tested this on our end in several browsers "Chrome, IE, FF, Maxthon, Safari, Opera" but as far as I can see it is working perfectly.

Do you happen to know what OS and Browser|Browser Versions they are using? If not then would you be able to possibly find out?

It could be a browser cache issue, a connection problem, or a problem with them using obsolete software and hardware though it is only theoretical at the moment.