Same Auth0 account and same DB,Different application sso

Same Auth0 account(tenant) and same DB,Two applications use Identity-provider-initiated SSO(SAML).

After application A successfully login with user name and password, click the trigger button to redirect(Through Identity Provider Login URL) into application B,this is successful. Click the trigger button again, but you can’t enter application B, it open the Identity Provider Login page directly,You must enter the user name and password to enter Application B.

I tried to use two different Auth0 account and create an individual applications.
No matter how many times the button is triggered, it can redirect to application B normally without login again.

What is the reason?