Start up issues

I have recently installed norton 360 Premium on 3 no. devises.1 on desktop pc 2 on iphone - both ok 3 on laptop.- ugghh.

When I power up laptop it goes into automatic repair etc. Can't reset, can't engage Safe Mode, the only input I achieve is Command Prompt. I have applied every solution from Google I can find to no avail. I have contacted Customer Help - what a total waste of time. the last response was that he wasn't a Windows expert and that I should contact Microsoft Help.The laptop was perfectly fine before I tried to instal  Norton 360. It ran on Windows 10 which I kept updated. The only solution I can think of now is to take it to an IT repair expert which will cost me about £60.00 - more than the Norton subscription.

Regards, Ron Shaw