Iphone 4as stuck in recovery mode, itunes not recognising device, iphone not turning on

I have iPhone 4s, its stuck in recovery mode loop with just the iTunes and cable symbol on front l it will flit to the apple symbol. Plugged it into iTunes, not being recognised by iTunes, have tried holding keys down, nothing, ran diagnostics test says iPhone not found, tried different cables, no joy, wont turn on at all just need to get the data off as phone not being used as a phone now.