2002 Echo...trunk issue

My trunk mysteriously won't open. When i pull the lever i can tell that
something is not catching and when I use my key i get the same feeling
of the latch moving but whatever mechanism opens the trunk isn't
catching. My husband is going to take the back seat off tonight (if we
can figure out how) and see if he can fix the issue by getting into the
trunk that way. Does anyone have any idea what could have caused this,
or how to fix it???

thanks for any input you can provide!! :)