Fix a Blank or Missing Microsoft 365 Sign-in Window

During Exchange Online setup in EdbMails, Microsoft opens a secure sign-in window to complete authentication. If that window does not appear, stays white, or stops loading, the problem is usually local to the Windows sign-in components, Microsoft Edge WebView2 Runtime, proxy configuration, or endpoint security controls. It does not necessarily indicate a mailbox or Microsoft 365 credential problem.

Use the checks below in order. Test the same work or school account at Microsoft 365 on the web first. If browser sign-in also fails, resolve the account, Conditional Access, or service issue before retrying EdbMails. For the migration workflow itself, see the Office 365 migration software page.

Resolution

Close EdbMails before changing system settings. Reopen it and retry the Exchange Online connection after each method so you can identify which change resolved the problem.

1. Method 1: Verify Microsoft Edge WebView2 Runtime

   • Open Control Panel and select Programs and Features. Confirm that Microsoft Edge WebView2 Runtime is listed.
   • Open the EdbMails Microsoft 365 sign-in window and check Task Manager for msedgewebview2.exe. A blank window with no WebView2 child process can indicate that the runtime is missing or blocked.
   • If the runtime is missing or damaged, install the current Evergreen Runtime from the official Microsoft WebView2 download page, restart Windows, and try again.
   • Do not assume that resetting the Microsoft Edge browser repairs WebView2. The browser and WebView2 Runtime are separate installations.

2. Method 2: Check automatic proxy detection

   • Click the Start menu, search for Internet Options, and open it.
   • Select the Connections tab, then choose LAN Settings.

     

   • If your organization does not require a manually configured proxy, enable Automatically detect settings and select OK.

     

   • If your organization uses a PAC file or authenticated proxy, keep the approved configuration and ask the network administrator to confirm that embedded WebView2 processes can use it.

3. Method 3: Reset Microsoft Edge settings when browser sign-in is also affected

   Use this method when Microsoft sign-in pages also fail or behave unexpectedly in the Edge browser. Resetting Edge restores browser startup, new-tab, search, and extension settings. It does not replace the WebView2 Runtime.

   1. Open Microsoft Edge.
   2. Select the three dots in the upper-right corner, then select Settings.

      

   3. From the left pane, select Reset settings.

      

   4. Select Restore settings to their default values.

      

   5. Review the confirmation message and select Reset.

      

   Restart EdbMails and retry the sign-in window. If Edge works but the embedded window remains blank, continue with the security and network checks.

4. Method 4: Isolate proxy, TLS inspection, and security controls

   • Temporarily test from an approved alternate connection, such as another business network or a mobile hotspot. Do not send mailbox data over an untrusted network.
   • If the sign-in window works on the alternate connection, return to the original network and review its proxy, firewall, SSL decryption, and certificate-trust configuration.

     

   • Ask the security administrator to check whether WDAC, AppLocker, antivirus, EDR, DLP, or browser-control software is blocking msedgewebview2.exe or the EdbMails host process.
   • Where TLS inspection is used, confirm that its certificate chain is trusted by Windows and that Microsoft authentication redirects are not being interrupted.

   Microsoft recommends scoped policy corrections for WebView2 instead of broadly disabling endpoint protection. See Microsoft's WebView2 security-tool guidance.

5. Method 5: Check DNS only when name resolution fails

   Changing DNS is useful only when the current resolver cannot resolve Microsoft authentication endpoints or returns an incorrect result. It is not a general repair for a blank sign-in renderer.

   • Confirm the problem with your network administrator before replacing an organization-managed DNS configuration.
   • Follow Microsoft's Windows TCP/IP settings guidance if a DNS change is approved.
   • Public resolver examples are shown below. Use a provider that meets your organization's security and compliance requirements.

     DNS provider	Preferred server	Alternative server
     Cloudflare	1.1.1.1	1.0.0.1
     Google	8.8.8.8	8.8.4.4
     OpenDNS	208.67.222.222	208.67.220.220

     

6. Method 6: Check Windows authentication components

   • Use this method when Outlook, OneDrive, Word, or other Microsoft 365 desktop applications also fail to open or complete authentication.
   • Run the Microsoft 365 Sign-in troubleshooter before manually changing Windows authentication packages or cached tokens.
   • Install pending Windows and Microsoft Edge WebView2 updates, restart the device, and test again.
   • If the device is managed, ask the administrator to review Windows Web Account Manager and Microsoft Entra broker events. Avoid deleting broker or token folders without an approved recovery procedure.

7. Validate the Microsoft 365 sign-in result

   • Reopen EdbMails and start the Exchange Online connection again.
   • Confirm that the Microsoft sign-in window renders the account page and accepts the required MFA or Conditional Access prompt.
   • Complete sign-in and verify that EdbMails can load the expected organization or mailbox selection screen.
   • Record the method that resolved the issue. If the window remains blank, collect the Windows version, WebView2 Runtime version, EdbMails version, timestamp, screenshot, and relevant Event Viewer entries before contacting support.

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Additional resources:

• Manual registration of EdbMails in Microsoft Entra ID
• Office 365 migration checklist
• Create a new Outlook profile for a single user
• Create a new Outlook profile for domain users
• App password guidance for supported legacy configurations