What voltage does the Dynon indicate when you fire the system up? Is your battery ground lug tight?
A couple of builders that have had trouble run a Battery Minder / 2 amp charger overnight to top off the battery then run the test. The trim should however, work in the lower voltage (12v-13v) mode so you can adjust the trim prior to take off.
RV-7 : In the hangar
RV-10 : In the hangar
RV-12 : Built and sold
RV-44 : 4 place helicopter on order.