Select Administrators under User Groups and grant full control to your admins and uncheck unwanted restrictions under "Deny".
If you are cannot access the User Groups tab, try to login as super administrator to verify the permissions of your Administrators group.
To login as super administrator, add this to your web.config under <appSettings>
:
<add key="MasterPassword" value="YourSecretPasswordHere" />
Then login with the user admin and the password you set.
And make sure to remove that setting after you sort things out.