My Flair 58 gauge needle does not return to "zero."

First, unscrew the gauge from the stem to try and release pressure: The o-ring in the stem pocket may just be displaced, preventing the needle from settling after brewing. 

If your gauge needle still does not return/rest at "zero" after brewing, then a replacement gauge is needed. This type of damage may occur if the gauge is dropped onto a hard surface (such as the counter or floor), or if you've brewed in the "danger zone." 

There is no way to recalibrate the gauge and ensure accuracy once this has occurred.