Longtime Head & Shoulders User Reports Worsening Dandruff After 15 Years of Use

For about 15 years, I've regularly used Head & Shoulders in its various forms, especially the menthol shampoo, every time I shower. However, over the past 4 months, I've been experiencing a noticeably increased dandruff problem on my scalp, and despite continuing to use the product consistently, the issue isn't improving.
Even though this has long been my brand of choice, the dandruff problem I've been dealing with recently is both bothering me and shaking my trust in the brand. For this reason, I'm requesting that the products I've been using be thoroughly examined, that a product exchange be made if necessary, and that my refund/situation be resolved if possible.
I'd like the company to check whether there's an issue with the product's ingredients or formulation, and to provide me with a clear, explanatory response.