We have looked and do not have “Enable Seamless SSO” option in Tenant → Settings → Advanced.
We are using the Auth0 Wordpress Plugin and we are using another vended app that supports SAML (via SAML Add-On for Auth0).
Using incognito, we can login to either one, and the other will prompt for login again. We tried both ways.
What are we missing?
Thank you for reaching out to us!
The Enable Seamless SSO is now only available for legacy tenants, for newer tenants this option is enabled by default, as mentioned in this documentation. After taking a look at your tenant, I can confirm that it is indeed enabled for it as well.
Another reason for SSO not working between applications is that the apps do not have the same Connection enabled. Please check and make sure you have at least one Connection enabled for both apps and test again if SSO works.
You can find more information on our Knowledge Article here.
Hope this helped!
Gerald
Hi team!
This is a heads-up that we’re hosting an Ask Me Anything (AMA) session dedicated to Auth0 sessions, refresh tokens, and the Management API. Our product experts will be on hand February 12, 2025, from 8 AM to 10 AM PST to answer all your questions—no matter how basic or advanced they may be! You can submit your queries anytime from now until February 11, and we’ll provide detailed written answers during the live event.
This is a fantastic opportunity to learn best practices around session management, refresh token rotation, and the Management API. Plus, everyone who participates gets points and a special badge just for joining in on the fun. 
If you have any burning questions (or even casual curiosities!), feel free to drop them in this thread. We can’t wait to see what you’re working on and how we can help you optimize your Auth0 setup. See you there!
Auth0 Community Ask Me Anything: Auth0 Sessions and Refresh Tokens