No audio on idvd burned disc- sound plays on TV fine but not on macbook DVD player

First time posting, so please excuse any naivete 🙂

Hi there, I'm having the opposite problem of many of the questions I've read on here- the audio on my burned disc won't play on my computer but is fine on my TV. I am running the latest version of idvd on a 2008 macbook. The music for the menu is a .m4a file (?) imported from itunes and the movie is an imported project from imovie. Both play fine in idvd preview and I have burned discs of this project before with no problems. This time I burned one disc through idvd, discovered the missing audio, deleted the encoded assets and re- encoded before saving the disk image and burning another dvd through disk utility. Both dvds are having this problem . I checked sound on my system preferences, it's on- though I can't find the "main audio" that was mentioned in another thread. Maybe I don't have enough space on my startup disk? I've been trashing some things to free up space, but I'm not sure where to check to see how much space I have.

I'm sending these dvds out as part of job applications so they need to be able to play right on whatever the reviewer uses (mac, pc, tv etc.)- is there a way to ensure it will work universally?

Thanks!