The Primary Webmaster is able to accept all membership requests, including requests to be a Webmaster.
Webmasters can accept all membership requests, except new Webmaster requests.
Team Admins can accept membership requests associated with the team they are an admin of.
If you can't accept a request, it is most likely due to you not having the correct permission in your Pitchero account.
You should contact your Primary Webmaster to moderate any outstanding requests if you are unable to do so.
To see how you moderate a member request click here.