I'm going to ask what might be a silly question... Have you checked your battery disconnect? Many times that gets pushed inadvertantly...when your battery disconnect is used, it, of course, disconnects the battery from everything in the TT...
If you don't have a disconnect (the '08s had them, not sure about yours) the other possibility is a blown fuse in the positive cable to the battery. If that is blown, it, too, effectively removes the battery from the system. The fuse is located in the black wire w/white stripe (pos terminal of battery), usually between the front bulkhead of the TT and the battery box...
My 2 cents, your mileage may vary...
2 Cats; J-Lo and Ragamuffin :R
2014 Thor Tuscany 40RX DP
2011 Ram 2500 Longhorn CTD HO
2011 Keystone Cougar 318SAB (now gone)
2008 FunFinder X 210WBS (Sadly gone)