I am vacuum bagging the hull of a boat and the sealing tape isn't sticking well to the fibreglass.  The fibreglass was laid 7 days ago. I have tried washing thoroughly with acetone and also a light sand, but tape is still not creating a good seal.  Any suggestions?  Does the fibreglass need to cure longer? Any assistance would be appreciated.

Does the tape literally fall off again, or are you just having problems to get a good seal?
Bagging tape is not as easy to use as it is shown in most videos. Usually you end up with some extra pressing around the tape to get it tight.
Unless you made some serious mistakes while mixing your resin, or you are using hot curing resin, your mould should be cured properly by now.