First of all, please consult the tutorial at the top of the submission form page on how to submit an abstract and check if you are doing everything correctly. You could be missing some information and that's why you can't submit.
If you see that you're doing everything correctly and you still can't submit, please try again by making the following adjustments:
- Use another device (if you are using an institutional device it may be blocking some access);
- Use another browser;
- Use a VPN (if you have it);