Hi Harry,
Thanks for posting your question here. I understand that you're trying to link your Curseforge account to your Microsoft account. This issue you're experiencing indicates an issue occurring during Microsoft account authentication process.
To try to fix it, please follow this:
- Open Edge or Chrome
- Go to: https://account.microsoft.com
- Sign out
- Close All browser windows
- Re-open the browser
- Sign in using only the Microsoft account you want linked
- Then try linking again from CurseForge
Avoid being signed into Xbox, Outlook, or Microsoft Store on a different account at the same time. Also, you may try to use a private/incognito browser.
Let me know if you have questions, I'm here to help.
Thanks,
Jobelle C.