Hi! So the way the tags work, you need to nominate them during the tag nomination period (this happens before the sign ups open) if you want to request them or offer them. That way they’re in the tag set so you can put them in your requests.

I just added Group: Peter Pevensie/Original Female Character to the tag set for you, so you should be able to finish that sign up now. Thank you for asking about it, and welcome!