If your fluid is full and clean - the first thing I would have checked is the switch that tells the transmission what gear you are selecting. This is normally not an issue on this vehicle, but it would still be the next step for me. After this, a test of the transmission assembly using a diagnostic tool would be necessary to see why engagement is not occurring. Doesn't sound very promising, to be honest.
fwd clutch piston, low servo ,low band ,if it go's in rev the low band is broken .CV not in gaged, oil pump shaft ,or valve body ,1 -2 ACCMM or O/D one way clutch or converter servo tubes out of case. It sounds like 2 weeks in Hawaii.also there are no elect that will cause a no engagement concern if you unplug the main harness from the trans it will go to limp mode elect will not pervent the trans from ingageing