I can't play my tapes back?

It could be several things -

*heavily used or badly knocked camcorder decks may have alignment problems
*the heads may be so worn (cleaning tapes are often like an ultra-fine sandpaper, so may have worn the heads out) that they are not up to the job any more
*the tapes may be worn out

I'd start by trying the tape in another person's deck, see if it works. If not, the tape is bin-fodder. If it's fine, take your deck to a pro/fix-it shop and ask

Paddy Robinson-Griffin
August 2007