Alpharma's professional help line.

He said the adhesive is similar to that used on Lidoderm.
The latter don't stick well either.

Some hints....
1) apply only to clean non oily skin that is very dry.
use alcohol if you have to remove oils, etc. first.

2) covering a curvey area, cut the patch into segments to
fit around the curve and use tape to hold it down.

Perspiration will affect the adhesion, causing the patch to slip off. The gel adhesive is very hygroscopic.

You might try the new Salonpas that were just approved by the
FDA OTC . They raised the methyl salicylate to 10% per patch and they are expensive. Available on drugstore.com

I use the older Salonpas OTC with success. Sometimes they stick too well, and they may cause a redness when removed.
I haven't tried the new ones yet...so I don't know what adhesive is used for them.

The manufacturer of Flector is aware of the poor adhesion. So is the maker of Lidoderm. But answers are not forthcoming.
Sorry.