I am new to macs, and love them, still troubleshooting though

I have four accounts on my computer myself (administrator) and three for my children and a guest.

The sound will not play on all the accounts and it is not consistent as to which account it plays on. Suggestions?

When we reboot the computer we can get sound on the first account logged into, then the other accounts will not play sound.

It is so frustrating!

Is there a setting I am missing?

Thank you in advance!