Normal users are not allowed to create checkers nor tags. This is covered in the FAQ:
What about the tags, can I create those?
In the past, anyone has been allowed to tag checker scripts with configurations and match them with challenge caches. However, this has changed now that Project-GC is an official part of the challenge cache framework. This is because we want to ensure that everything is working as intended.
Everyone who has created a checker tag in the past has been added into the permission list to be allowed to continue creating tags.
At this time, if you need a challenge checker or tag, you need to start a topic in the Challenge checkers forum.