'This PC is ready for Windows 11' but not getting the update

Solution 1:

It depends on the PC, EVEN if the computer is exactly same, it depends. The windows update is preparing update for your PC. Then after sometime, It will appear as a optional update. Waiting is recommended, BUT if you want to upgrade now, use this app: Windows 11 Installation Assistant. To use it scroll down and select Download Now under Windows 11 Installation Assistant. It will guide you to install Windows 11.

Solution 2:

Microsoft is rolling out big updates slowly, so that servers are not overloaded and if any bugs are caught, not everyone is affected.

Solution 3:

The Windows blog have more details

new eligible devices will be offered the upgrade first. The upgrade will then roll out over time to in-market devices based on intelligence models that consider hardware eligibility, reliability metrics, age of device and other factors that impact the upgrade experience. We expect all eligible devices to be offered the free upgrade to Windows 11 by mid-2022)

That is, your device meets the minimum requirements and should get the upgrade offer somewhere between now and mid-2022. However, Microsoft deliberately only pushes to the hardware they've actually tested and verified to work, then slowly expands to other similar models or perhaps those they proactively acquire and test. In the meantime, they will also release updates to fix the bugs they found.

This way they minimized the "Windows upgrade broke my PC" incidents from untested hardware combination, but you can skip the queue and install it right away with the assistant, taking the risk that your hardware turns out to be the problematic ones. The problems you encounter (if any) would then be fixed by a later update, and once everything works, PCs similar to yours will get their offer.