Chosen Solution

The button to turn on my phone has stopped working (right hand side at the top). Phone is fully charged but will not turn on.

Hi, Try a power refresh and check if that resolves the problem. Remove the battery from the phone and then press and hold the Power On button for a full 30 seconds and then release it.Reinsert the battery and then try pressing the Power button and check if it turns on. Here’s the ifixit Samsung Galaxy S5 Sport Battery Replacement guide that will help.