After working well for about 18 monthh, OTAdvancedAuthentication stopped working about 1 year ago on my iPhone 8, now running iOS 15.1. OTAdvancedAuthentication tries to launch, there is a very brief flash, and then it disappears and cannot be found. The two factor authentication codes have no way of being received. I have deleted OTAdvancedAuthentication and re-download it from OTAdvancedAuthentication Store several times, but that has not fixed anything. This has been in the reviews for over a year, so I can only believe that the developers are no longer supporting this product. Unfortunately it doesn’t seem to matter to my company, leaving me in a very difficult situation. I am only posting this review to help inform others who may experience this.