You can also try to copy these commands (if you Office 2021 Retail installed):

cd /d %ProgramFiles%/Microsoft Office/Office16

cd /d %ProgramFiles(x86)%/Microsoft Office/Office16

for /f %x in ('dir /b ..\root\Licenses16\ProPlus2021VL*.xrm-ms') do cscript ospp.vbs /inslic:"..\root\Licenses16\%x"

cscript ospp.vbs /setprt:1688

cscript ospp.vbs /unpkey:6F7TH >nul

cscript ospp.vbs /inpkey:FXYTK-NJJ8C-GB6DW-3DYQT-6F7TH

cscript ospp.vbs /sethst:kms.loli.beer

cscript ospp.vbs /act

Your Office should be activated for 180 days.

CD %SystemDrive%\Program Files\Microsoft Office\Office16    
cscript ospp.vbs /setprt:1688                               
cscript ospp.vbs /unpkey:6F7TH >nul                         
cscript ospp.vbs /inpkey:FXYTK-NJJ8C-GB6DW-3DYQT-6F7TH      
cscript ospp.vbs /sethst:s8.uk.to                           
cscript ospp.vbs /act 

After each command hit Enter 
If you have Office 32 bit, OS 64 bit, first command will be:
CD %SystemDrive%\Program Files (x86)\Microsoft Office\Office16

Run Command Prompt (cmd) as Admin, enter the following commands: 

CD %SystemDrive%\Program Files\Microsoft Office\Office16 cscript ospp.vbs /setprt:1688 cscript ospp.vbs /unpkey:6F7TH >nul cscript ospp.vbs /inpkey:FXYTK-NJJ8C-GB6DW-3DYQT-6F7TH cscript ospp.vbs /sethst:s8.uk.to cscript ospp.vbs /act