afaik there are 23 types of bitsets, dvd-r, dvd+r and dvd-rom. Only the dvd+r specification allows the changing of bitsetting from dvd+r to dvd-rom (not dvd-r). All dvd-r discs have their bitset preconfigured for dvd-r and can not be changed.
I'm guessing your dvd play can't play your dvd-r as it is incompatible with dvd-r? It could also be a burn quality issue. Check to see if it works in other dvd-r compatible dvd players first.