Athletes should be able to register for your competition if you have "launched" it (aka published it) and the registration period is currently open.
Follow these steps, to check it:
Verify you published your competition:
In the list of your competitions, next to the published ones will write. Published, and next to the unpublished ones Set Programming.
If your competition is unpublished, finish programming and publish it.
Verify your competition registration period is currently open:
Open the competition Dashboard.
Select Registration > Dates.
Verify dates and times and click Save.
If the registration period is open, and athletes still can’t register, please ask them for a screenshot of the specific error message they may see on the screen before contacting us through the in-app support chat.
Without sufficient relevant context, we may not have enough information to resolve the matter.