Thanks for following the link. In the future you will be able to see forms that your dentist would like you to fill out ahead of your visit, see treatments that the dentist has suggested, or even pay your bills.
Unfortunately right now your portal page is not ready. There may be a problem with the data that your dentist has on record for you or maybe there was just an internet glitch. Please have a chat with the reception team when you go in for your next dental appointment, and hopefully they can resolve the problem so that the portal is ready for you next time.