Force 4 boats were made of PVC
Now owned by Sensation Yachts in New Zealand. As far as I know, Force 4 only used PVC in their recreational tenders.
I do not know of a US agent for them any more. Defender was the last one I remember selling their boats. That goes back about 5 years.....
You can probably contact Defender's service for some advice. This is what I would do: you'll want to use a two-part Bostik glue, for PVC fabric, clean with MEK before re-installing. Rough up the fabric (both sides) if it was not done at the factory (may be why it came off in the first place).