i think it needs a service but it had a lovely soound and now i cant get my high notes no more

If your high notes are giving you problems-check the way your mouth is positioned on the mouthpeice. If you are positioned the same way you were before this problem-then just give it time. Tone problems on higher notes go away by themselves sometimes; almost as quickly as they come. If it is a consitant problem and your tone and stuff is alright, then take the flute in and see if there is a minor problem. Usualy it is the player, though, and not the flute-so look at what you are doing when you are trying the higher notes.

The crown cork is possibly leaking or well out of position, or there is a space between the cork and the metal disc at the embouchure hole end of the cork.

I had been practicing a (difficult) piece all week and it was practically perfect--my high notes were no trouble at all. Then, I played it on the weekend and I struggled. My suggestion is do plenty of flute warm-ups and begin practice; then have a 15 min break and resume. You`ll be much better. I was.