I had the same problem for a while, you should check to make sure you dont have any other story arcs running.
hmmm .. do you meen current lvl Arcs or any past story arcs, as i have a few low lvl ones still on the list ...
I'll just have to clear them out and see.
You can only have 2 full arcs open at once. It's a pain to clear them, but it's the only way to get new ones.
Be aware though that you can have as many zone arcs open as you like so you don't need to close them off.
Full arcs show a gold book
Zone Arcs a redish book and include the ones in The Hollows, Striga, Croatoa, The Shadow Shard, Rikti Warzone, Paragon Uni and Faultline ones IIRC
From my experience you must not have more than 1 open story arcs before you speak to Maria. If you have started the missions from maria while still having 2 arcs open then clear an arc and go back to Maria she does not open her arc.
Thats my personal experience from doing Maria on 9 alts at her level. The only time she gave me the Statemans Pal mission was when I started the arc with a free arc slot available. Retrospectively completing and old arc and going back to Maria half way through her missions has not opened the arc or given me the rescuse Statesman.
This has caused me a few "ohhhhhh shhhhh......uuuugggaarrr"
moments when I have started the arc without actually checking I was clear of old arcs 
Thanks so much for the info guys, i did have 2 full Arcs open and on completing one i can go back to Maria and carry on the missions for her Arc 
It was a real thorn in my side as not many people ever advertise for having Statesman's Pal on the UBH Channel and its one i really wanted. And now i can get it
Can someone please shed some light as to why i cannot get the mission to defeat Tyrant to be granted the Statesman's Pal Badge
My memory is a little hazy as i had parked my PB at lvl48 for about 2 months to help lvl my girlfriend up so we could ding 50 together .. i thought it would be a nice ending to get from 49-50 with the final lot of AVs and Tyrant, as im sure Maria tells you that you must come back to her at a higher lvl to do the run up to Tyrant.
I have done all of the missions for Maria Jenkins to get the Dimensional Warder Badge, but never got to do the missions where there are 2 AVs in each mission as i remember doing so on my Scrapper and these were all done at lvl50 with him.
Hope someone can give an idea of where i went wrong, so as not to repeat the same in the future.