Not every player will play BD-R. Also depends if the client’s client has current updates on the player. Are this discs you burned personally and tested? In fact, who is this person saying your discs dont work and are they smart enough to know to play them in a BD player? – Ha Ha
This is a common problem with burned BD-Rs and just sending them out willy nilly to whomever. DVD was the same way in the early days. its always important to let the client know that BD-R is not 100% compatible.
Find out the player and make sure they have current firmware updates and go from there.