I really liked your track! Don’t know why they didn’t accept it.
The only thing i realized is the fadeout at the end of the song. You can hear the strings being cut off at the end, i would use a longer note and some longer fade out.
I would try using something that sounds less like a pad for strings and try something more natural like a “solo violin” with some reverb or delay to create some depth. Maybe that way will change the reviewer mind? 
A piano is not an acoustic guitar.
Hello!
The notes of the piano break not very nicely.
Pianos need more effects.
In general, I liked everything! Good luck!