Often times the reason for lack of adhesion, which is usually what this question ends up being related to, has to do with surface preparation. A lot of times people don’t realize that the surfaces they might be working with can be contaminated.

For instance, if you’re talking about a plastic part, there may be mold release on the plastic part that was helped to use unmold the product when it was being manufactured. If that mold release is not removed then the tape is actually being asked to adhere to the mold release instead of the plastic itself.

That can interfere with adhesion. Particularly with metal products, you sometimes have oils that are used in order to prevent corrosion or the formation of rust. Sometimes those oils are not removed prior to the tape being applied, so you end up with an interference there between the adhesive system and the metal surface.

There can also be, depending on the manufacturing environment, there can be dust or contamination that may be naturally occuring in that manufacturing environment. If that contamination is not removed prior to the application of the tape that can interfere as well.