Try this: Go to Google Chrome (if that is your browser) tap it to open, scroll to settings, tap that and scroll to Site Settings, tap that and scroll down to Pop Ups and redirects and make sure that is toggled to Blocked. Then hit All Sites, and find the site you're having issues with, tap on it and hit either delete for stored data under Useage or Clear & Reset under Permissions. I've had success with this when having problems with pop up ads on various websites.