This mod can ONLY block those useragents that you have entered in the list, firstly get your user to go here
http://whatsmyuseragent.com/ (via his phone) and find out what his useragent is then you go here
http://www.botsvsbrowsers.com/SimulateUserAgent.asp and paste his UA string in and test it to see if you get denied or not.
Something in his useragent string is in your list so it's not the mods fault as it's banning what you ask it to