During the app installation, it adds some code to your theme templates. If you installed a new theme after the app, it will miss the required code and the app will not work.
So please go to Apps - EasyAuth - Installation and click the "Enable" button next to the name of your new theme.
If it doesn't help, please grant our support team access to your Store Admin, and we'll add the required code to your templates, and make sure app is working properly. Please send an invitation to email@example.com and let us know once done via email.