How to Fix Office 365 Pro Plus Error CAA50021: Device Registration Issue. This error may occur in any Office 365 Pro Plus desktop application.

We weren`t able to register your device and add your account to Windows. Your access to org resources may be limited.

Solution 1 Command Prompt (CMD)

Better use the Command prompt because Windows PowerShell does not understand %ProgramFiles(x86)% in command. But the solution can be completed in both CMD and PowerShell.

1. Run Command Prompt or PowerShell

2. At appeared Command Prompt application right mouse button click and select Run as administrator;

3. Type the following command:

cscript.exe "%ProgramFiles(x86)%\Microsoft Office\Office16\ospp.vbs" /dstatus

4. After that, you get some information about Office installation and:

Last 5 characters of installed product key: XXXXX

5. Type the following command, where XXXXX – your last 5 characters of the installed product key:

cscript.exe "%ProgramFiles(x86)%\Microsoft Office\Office16\ospp.vbs" /unpkey:XXXXX

Solution 2 (Windows PowerShell)

1. Right Mouse button click on the Start button and run Windows PowerShell (Admin);

2. Type the following command:

cscript.exe "C:\Program Files (x86)\Microsoft Office\Office16\ospp.vbs" /dstatus

3. After that, you get some information about Office installation and:

Last 5 characters of installed product key: XXXXX

4. Type the following command, where XXXXX – your last 5 characters of the installed product key:

cscript.exe "C:\Program Files (x86)\Microsoft Office\Office16\ospp.vbs" /unpkey:XXXXX

Solution 3 (Registry Editor)

Change Registry to disable modern authentication for office applications.

1. Click on Start button and type:

regedit

2. At appeared Registry Editor application right mouse button click and select Run as administrator;

3. Navigate to:

HKCU\SOFTWARE\Microsoft\Office\16.0\Common\Identity\

4. And set key EnableADAL REG_DWORD to Value: 0