Login errors are most commonly the result of content blockers (adblockers) in the browser. Try disabling any adblock extensions and clearing cookies in your default browser.
If that doesn’t work, then in a different browser, navigate to our accounts page here. Try signing in there - do you have the same issue with single-sign-on? If not, then sign fully out of your account before opening Roon and trying again.
Did you set the Roon Server software to Launch at Startup (of your computer)?
There two Roon programs loaded on your laptop, ie. Roon Server and Roon (client). Go to your computer taskbar and right click on Roon. You may need to click on the little up arrow first. It takes the Roon server a minute or two to open before you can open Roon (the client).
What I just posted applies to a Windows computer. A Mac will be slightly different.