Windows 2019 update says “device isn't quite ready for it” – what exactly do they mean?

When doing a windows update, I get the following message:

The Windows 10 May 2019 Update is on its way. We're offering this update to compatible devices, but your device isn't quite ready for it. Once your device is ready, you'll see the update available on this page. There's nothing you need to do at this time.

Does this mean that version 1903 for my PC is not yet ready or does it mean that I will have to change something in my PC to make it ready?

Does this mean that version 1903 for my PC is not yet ready or does it mean that I will have to change something in my PC to make it ready?

It means your device, at this time, is not compatible with 1903. This might be due to the software you have installed or there is a hardware incompatibility that currently exists.

You simply have to wait until the reason 1903 is blocked is resolved by Microsoft.

On machines that have the upgrade path blocked for some reason, users will be notified that the update is available, but that their PC is not ready to take it yet.

The report states that the message is already being displayed on incompatible machines that search for updates, so other users should start seeing the warning as well.

It is well know that Microsoft has the ability to prevent feature updates when it flags anything that might be incompatible with the feature update.

One of these blockers was if software that uses an incompatible version of an Anti-Cheat Framework was installed. Microsoft considered the GSOD that was caused by the incompatible Anti-Cheat framework to be serious enough to block 1903 from being installed.

Update Assistant, Media Creation Tool, and Windows Update will all inform you of this incompatibility with a feature update and either rollback the installation of feature update or prevent the installation from proceeding entirely.

Eventually, the reason the feature update is being blocked from being installed on your machine, will be resolved. Once Microsoft lifts the block 1903 will be offered to your machine and will be installed without an issue automatically.

Source: Microsoft Finally Gets Rid of Anti-Cheat GSOD – Upgrade Block to Be Lifted Soon

Source: It means your device, at this time, is not compatible with 1903