Hello, Here are some ways to fix it : '''Set default browser manually''' Open the Start Menu and click the Settings gear icon. Go to Apps > Default apps. Scroll down to find Web browser (or search for firefox). Click on the current browser and select firefox from the list. '''Disable administrator mode for firefox''' Close firefox. Right-click your Firefox desktop shortcut and select Properties. Go to the compatibility tab. Uncheck "Run this program as an administrator". Click Apply and OK. '''Stop the message dialog''' Open firefox and type about:config in the address bar (accept the risk warning). Search for '''browser.shell.checkDefaultBrowser''' Double-click it to set it to false. If there is still an issue, try refreshing firefox or doing a reinstallation of firefox.