If it says "You do not have the permission to execute that command" it usually means that your gm dosnt have enough gm previlegies, have a look at your commands.xml, groups database, players database and accounts database, and make sure your GM character is in the right group, that said group has a proper access, and that your gm's account is the proper account type according to the commands.xml
For example, if the /a command requires type=5 and access=6, make sure your gm's account has account type 5, and that the group your GM char is in, has access 6.