Issue with Power BI Desktop serverside authentication

Hi Erkko ,
Thanks for reaching out to Forum Community.

Recurring sign-in prompts in Power BI Desktop usually happen when accounts or tokens don’t match. Make sure your Windows login, Desktop sign-in, and installation account are the same. If needed, add your Power BI account via Windows Settings - Accounts - Access work or school, and clear old credentials in Desktop (File - Options - Data Source Settings - Clear Permissions) and Windows Credential Manager. Reinstalling Desktop under the correct profile and launching with the intended account also helps.

Also, check Integrated Windows Authentication in Internet Options and review organizational policies like Conditional Access, MFA, or Hybrid Azure AD Join. Signing in first via Edge - Office 365 - Power BI Service can help Desktop recognize your token and stop repeated prompts.