IThemes + Security Giving White Screen for Login

Recently I inherited a website and did an update on their massively out of date WordPress + plugins. This promptly made it so that the IThemes custom login page was now going to a blank screen. In fact, the only way to get a login screen at all was to go into the FTP and rename the theme+plugins folders to disable all the plugins and the theme which allowed the original wp-login.php screen to work. Is anyone else having this issue or can help me figure out how to resolve this issue?

Thank you!