iPhone safari redirect issue

When I go login my username and password on prudential.com and click a link to send me to a self managed portion of my account safari opens a new tab at bny Mellon and asks me for login info again. Which is supposed to be linked to the first login at prudential so it’s basically a dead link and I can’t open that portion of my account. This only happens on iPhone 6 Plus. Website and services work fine on MacBook and iPhone X. Both prudential and bny said update phone which I am running 12.4.6 which is latest update. So I feel it is a software issue with safari or Apple.