Some users have reported that they are unable to select "Remember for 30 days" in their internet browsers while authenticating using DUO. When users attempt to select this checkbox, it displays a "no" sign and the user is unable to select this option. This is caused when a user set one of their devices to automatically use a default method of authentication. This feature was removed by DUO and is no longer supported. Once you delete the device that was set as the default authentication method for DUO and re-add it, you should be able to select the Remember for 30 Days checkbox once again.