I have a similar issue. I have a premium (paid) account with Dashlane. The extension is turned on in Brave. I am able to login via the extension in Brave. The issue is when I go to click on “Open App” in the Dashlane extension window, a blank “untitled” tab is opened behind the current tab. When I go to that “untitled” tab, no information is displayed. I have the Dashlane app installed on my computer. To my understanding, the desktop app is suppose to launch. At least it did that in the trial period before I upgraded to the paid account.
Also, not certain if this is a Brave issue or Dashlane issue. In the same Dashlane extension via the Brave browser, when clicking on the Dashlane icon to login, the password field loads and the “Show” button to show the password does not reveal the visual password when pressed. All that shows are the **** of the entered password. So, if I misspelled the password, I’m not able to view what was entered.