yes, Billy is right, we need more details, what is exactly the error message? because "doesn't open up" is very generic. But generally, when something works for one person and doesn't work for another it's always that particular computer or smartphone related. Something in the settings. Because if it was on the site's end, nobody would be able to send messages.
For one thing I know: this site is barely usable with Opera-Mini. It has a lot of Ajax elements, and Opera-Mini doesn't work well with Ajax. So, if you use Opera-Mini, try another browser.