>>106275908
>>106275959
>>106278027
>>106283942
MS updated the code signing algorithm to SHA-2. On Win7 you have to install KB4490628 and KB4474419 before Windows Update will work.
The other issue is that there are so many updates for Windows (before they switched to the monthly cumulative system) that PCs take a long time to parse the update catalog on the initial check for updates.
Your best bet is to install the last major updates by manually downloading them and installing them offline, then use Windows Update. But even on a high-end system Windows Update takes at least 20 minutes to parse the update catalog.
Major updates:
IE11 (KB2841134) - Get the ~22MB offline installer
2019-12 Servicing Stack Update (KB4531786)
2019-12 Cumulative Security Update for Internet Explorer 11 (KB4530677)
2020-01 Preview of Monthly Quality Rollup (KB4539601)
2019-12 Security and Quality Rollup for .NET Framework 3.5.1 (KB4533095)
Malicious Software Removal Tool (KB890830)