I am attempting to set up a command block that would promote the player to "Member" rank. I have already enabled allow commandblocks in the groupmanager config and I have enabled command blocks in the server settings. I have managed to be able to promote myself using the command block however the moment i chnage my username to @p it no longer works.
More than likely you need to actually enable command blocks. (I would not advise this). If you would like to enable command blocks, you need to open your server.properties file and edit the line that says "enable-command-block=false" and change it to true "enable-command-block=true"
Can you tell me what it is you are trying to accomplish with a command block controlling your server permissions and ranks?