I am guessing you are switching a website to your Tealium training account?
In that case, try the following;
1. Use a browser where you can clear the cookies freely (e.g. a separate Chrome profile https://www.bettercloud.com/monitor/the-academy/how-to-create-switch-profiles-in-chrome/)
Install Tealium Tools in this separate browser or Chrome profile.
2. Go to the home page of the website (and not the page that pops up a "switcher")
3. Use the Tealium Environment Switcher to switch to your training account and profile. https://community.tealiumiq.com/t5/iQ-Tag-Management/Tealium-Tools-Environment-Switcher/ta-p/16027
4. Clear the browser's cookies, including 3rd party ones (so do this via browser settings)
You should now be good to go.