Open developer tools and go to the "Application" tab like what's shown in the attached screenshot. (You have to right-click on the page and select "Inspect" from the menu to access the developer tools. Then, if you don't see "Application," you click on the two arrows and get a dropdown menu where you should see "Application" as I did in the attached screenshot.)
When the Application screen opens, you should see a "Cookies" option on the left side panel. Click on that if the dropdown isn't already opened to show you the member panel domain name/URL.
Right-click on the member domain URL and click on "Clear." (screenshot attached)
Exit the "inspect" menu by clicking on the 'X' in the top right of the menu (not the browser window).
Refresh the page and try to login again.
If the above steps don't work, try with an Incognito window.