Muse not working

I’ve had my Muse 2 handset for the past two months. Used it almost every day during that time yesterday I recharged it all seem to be okay however this morning when I went to switch it on for my meditation session it would not start the light remains black.
I assumed that I must have left it on accidentally previously so that it was flattened again. so I put it back onto charge thinking no more about it.

This morning it still won’t activate dispute being recharged. I seen this forum that there is a means of resetting the headset if this type of problem occurs. So I held down the start button for 15 seconds. This has not resolved the issue and the device still won’t activate.

When I connected to the charger the array of lights pulses very slowly in unison so I’m assuming it is charging but as I mentioned earlier it won’t activate when I disconnect the charger and try to start the device. Anybody or three suggestions on how to get the device working again.