Lots of problems can be caused by cookies not working on your machine. Make sure your browser (Safari, Firefox etc.) has cookies turned on, so you are accepting them. This tends to be the main problem when using iPads.
With an iPad, go to Settings / Safari / Accept cookies – From visited (or Always)
Apple’s advice for using Safari on iPad
There are two things that are most likely stopping the chat system from working. They are quite tetchy so you may want to refer your IT support technician to this page:
2. Many schools use net filters based on keywords such as chat. Please ask for http://www.imascientist.org.au to be whitelisted.
Please contact us on firstname.lastname@example.org or +61 (0)410 442 629 if you’ve checked this and it still doesn’t work.