I want to allow registration for my runner so they can finalise their place but the option isn’t available.

Check the application of the runner, if in column ‘Own Place’ you can see YES, the runner has stated they have their own place you will not need to give them a place. Tip: Confirm with the runner that this is correct. If the runner made a mistake on their application you can raise a ticket here and request the application is updated. Following this action the runners status will be put back to 'reviewed' allowing you to once again 'Accept' the runner which this time will allocate a place from your availability. From there you can 'Allow registration'
Check how many places you have available in the breakdown section at the top of the page. If all your places have been allocated you will not be able to accept any further applications.
Entry codes may not yet be available for the event at hand, you will receive a communication from the team at realbuzz as to when these entry codes will be live after which, unless the above applies to the runner, you will be able to 'Allow Registration'.

The Allow Registration option may not be available for a few reasons, troubleshoot it here.