robertoriginal what gauge strings are you using?is your tuner loose?and or, is your trem set up wrong? i.e. your tension bar may be too high.
Doog Try tuning it, and giving the string a good stretch away from the neck at the 12th fret- it may just not have seated properly.
Aug Possibilities:hanging on nut (unlikely)string slipping in the tunersaddle moving (unlikely)string not properly stretched (like doog said)string's ball end not properly seated in the tremolo bar. 😁
Veryape I have changed my strings but that was two weeks ago and I play for an hour every day. But I will check that anyway.Thanks