This question is similar, but deals with intact tape: Removing Tuck Tape from an unfinished window frame
In my case, it has been out in the sun for some time on PVC siding window trim. One side was in shade and I could get the tape off, then Goo Gone worked well to take off the stuck adhesive.
On the other side the tape is brittle and has little strength. So far the largest piece I've gotten off is about 1 cm2. Goo gone doesn't seem to go through the tape. Ideas?