After login to my club website, a page displayedin a new tab drops the login

After logging in to my website (having public and restricted content), all pages displaying in a separate tab recognize my login credentials except our Calendar page. It “forgets” that I am already logged in and forces me to use other pages to access restricted pages and functions.

Browsing our site using MS Edge and Googls Chrome does not present this problem. I can not find an optin in Brave settings that will resolve this issue. Suggestions welcome.