can't download Office 2021 through setup.office.com. When I click the link for the 64-bit OR 32-bit version, it tells me "service unavailable"

Hii,

If the license you are trying to use is LTSC, in this case you will need to uninstall office and you will need the .xml file to generate the LTSC installation.

https://learn.microsoft.com/en-us/office/troubleshoot/installation/how-to-download-office-install-not-in-vlsc

In this case, you will need to extract the files from the office offline img and place the configuration .xml file and run the office installation with prompt on command (admin) in the folder where you extracted office 2021.

Here is an example of the xml file to install office 2021 ltsc.

<Configuration>

  <Add OfficeClientEdition="64" Channel="PerpetualVL2021">
    <Product ID="ProPlus2021Volume">
      <Language ID="en-us" />
      <ExcludeApp ID="Lync" />
    </Product>
  </Add>

  <Remove All="True" />

  <!--  <RemoveMSI All="True" /> -->

  <!--  <Display Level="None" AcceptEULA="TRUE" />  -->

  <!--  <Property Name="AUTOACTIVATE" Value="1" />  -->

</Configuration>

You will open the on commando prompt (Admin) in the folder where you extracted it and run the command: setup.exe /configure configurationx64.xml.

After installation, open an office application > files > accounts > change product key and enter the key you have.

Give feedback if the information was useful or not.

Thanks

Hii,

The offline installation of Office 2021 is available at the link below:

https://officecdn.microsoft.com/db/492350F6-3A01-4F97-B9C0-C7C6DDF67D60/media/en-US/HomeBusiness2021Retail.img

After the download is complete, disconnect from the internet > right-click > select Mount > go to File Explorer > My Computer > select the Office icon > right-click > Open > go to the Office folder > go to setup64

After installing, you will open an Office application and it will ask for the 25-digit license or the Microsoft account that owns the license.

Give feedback if the information was useful or not.

Thanks