As of today my wife's S5 refuses to play any video's she has filmed, either new ones today or previously ok ones stored. The video's play on other phones and this phone will play online video's from youtube etc, so we are a bit baffled.

Not sure if there is a way of checking if there is/was a default video player or if she needs to reinstall the app, or is there a restore to yesterday thing like in Windows? She has never installed any other apps for this, it is only the one that was on the phone originally, any suggestions would be a help......

Try downloading the vlc app from the app store.

It works with downloaded videos so should work with your issue.

We have considered that and probably will, but I look at that as a work around, what puzzles me is why this has happened. I mean there's no good reason why it shouldn't play its own shot/stored footage. like it was doing two days ago!