Hi @Abdallah Mohamed
Did you install and activate Office Professional Plus 2021 on other machines?
- If not, have you redeemed the Office via bound your account to this product key when you open the Office app first time?
Please note, the message says: "the specified Product Key has already been activated the maximum number ---", for one-time Payment versions of Office, it can be only installed on one machine, if you want to transfer it to another one, you will get such message.
So, I suggest you contact the seller, and report this issue.
It is also possible that your device may not be able to connect to Microsoft's servers that causes this issue.
- I suggest you try the following commands in Windows Command Prompt.
- Search CMD, right-click the Command Prompt and run as administrator. Then copy and paste the command below in it, click Enter at last:
cscript.exe "%ProgramFiles%\Microsoft Office\Office16\ospp.vbs" /dstatus
- Please remove the "Last 5 characters of installed product key" (I replace it with XXXXX, but what you type in is what you see on your computer) in this interface:
cscript.exe "%ProgramFiles%\Microsoft Office\Office16\ospp.vbs" /unpkey:XXXXX
- And then enter the new product key that you bought:
cscript.exe "%ProgramFiles%\Microsoft Office\Office16\ospp.vbs" /inpkey:AAAAABBBBBCCCCCDDDDDEEEEE
- You may also contact Microsoft Support on chat via link: https://support.microsoft.com/en-us/home/contact?
If the answer is helpful, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment".
Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.