No sound on apps for I phone

[ledkr]

Hi. I have purchased two apps now which should have sound. One was the Davina McCall fitness app free didn't play now the upgrade doesn't and a times table app for dd which even asks you to select a male or female voice but is silent.
Any suggestions?
All other sound is fine. The Davina one even eats you select from my play lists and plays them fine when I do. I can see her lips moving but no sound.

Have you tried deleting them then readding them. Works on my ipad if I have problems with apps.

I lost all sound on my iphone, restored factory settings and it was sorted, although I had to reset ringtone etc.

Have you set your media volume to zero by mistake? Try going into the settings and looking at all of the different volume levels.

Oh no that makes no sense if some parts are working I have no idea!

Have you tried switching it fully off and on again (I know, it's a cliche but only because it often works!)

Did all the above! No change. Not sure what it is maybe they download in the wrong format?
Any other knowledge?