Hi Joanna,
I can help you get back in fast. What you bought from OnTheHub is Office Professional Plus 2019. That edition uses a volume key and is not tied to your Microsoft account. After a Windows or hardware change it can drop its activation and show Not activated. The quickest fix is to reactivate it with your existing key using Office's built-in script.
First, open an elevated Command Prompt. Click Start, type cmd, right click Command Prompt, choose Run as administrator.
Next, run the activation commands below. Use the path that exists on your PC. On 64-bit Office try the first line. If it says The system cannot find the path specified, use the second line instead for 32-bit Office on 64-bit Windows.
cscript.exe "C:\Program Files\Microsoft Office\root\Office16\OSPP.VBS" /dstatus
cscript.exe "C:\Program Files\Microsoft Office\root\Office16\OSPP.VBS" /inpkey:XXXXX-XXXXX-XXXXX-XXXXX-XXXXX
cscript.exe "C:\Program Files\Microsoft Office\root\Office16\OSPP.VBS" /act
If the folder above does not exist, try:
cscript.exe "C:\Program Files (x86)\Microsoft Office\root\Office16\OSPP.VBS" /dstatus
cscript.exe "C:\Program Files (x86)\Microsoft Office\root\Office16\OSPP.VBS" /inpkey:XXXXX-XXXXX-XXXXX-XXXXX-XXXXX
cscript.exe "C:\Program Files (x86)\Microsoft Office\root\Office16\OSPP.VBS" /act
Replace the XXXXX-XXXXX-XXXXX-XXXXX-XXXXX with your OnTheHub product key. After the /act step you should see Product activation successful. Then open Word, go to File > Account, and you should see Product Activated.
If you get an error instead, tell me the exact code that appears in the Command Prompt window. With that code I will guide you to the next step.