Jeffa, the most common cause is battery wires get crossed and the resettable breaker/fuse along the tongue sets off.
there are numerous threads, about this issue, with pics of the breaker/fuse.
here's a link to a recent one:
it's between the battery and the front of the trailer. follow the wires along the tongue.
by the way, you have a hybrid/expandable and there is a section here for that type of trailer, with a Shamrock sub-section.
you posted in the regular TT and 5th wheel section.
also, the Roo hybrid is a twin of the Shamrock, so that sub-section can also have info for your Shamrock.
and Zoe the Wonder Dog(R.I.P.)
'07 Roo 23SS pushing an '07 Chevy Avalanche
Equalizer WDH and Prodigy BC