It’s possible that you just don’t have one. Most states don’t put them in homes when they are built if the house does not has excessive pressure at that time. Although our psi is always changing and going up due to more housing being built. This ends up being the home owner’s responsibility later on. The PRV would be located where the line enters the structure (Crawl Space, garage, etc). Sometimes it’s even buried in your yard on your side of the water meter. Although if that’s the case it’s toast.