Hello,
You need to add the following Windows Update website addresses to the "Allow" list. The Windows Update service connects to the Internet through port 80 and port 443.
http://windowsupdate.microsoft.com
http://*.windowsupdate.microsoft.com
https://*.windowsupdate.microsoft.com
http://*.update.microsoft.com
https://*.update.microsoft.com
http://*.windowsupdate.com
http://download.windowsupdate.com
http://*.download.windowsupdate.com
http://ntservicepack.microsoft.com
You can refer to the following links:
Step 2 - Configure WSUS | Microsoft Learn
I hope the information above is helpful.
Best Regards
Zunhui