As of Version V20 Update 3 i can no longer simulate my unified hmi.
Project complies without errors but when “downloading to device” i get the following error:

Start downloading to device.

HMI,

Download to simulated Runtime is being executed.

A full download is required because this project is not available in Runtime.

Runtime "HMI" can be started after download.

Keep values of tags, active alarms and user management data.

Keep current values of tags and pending alarms in the runtime.

Keep current user administration data in runtime.

All logs such as tag logs, alarm logs, audit trails, and context logs are reset in runtime.

The Runtime has the following version: V20.0.0.2.

The firmware has the following version: no image version.

To prevent unauthorized access during loading, activate encrypted transfer for simulation in WinCC

Unified Configuration of this PC and in TIA Portal under 'Options >Settings >Simulation > HMI Simulation'.

The configuration data of the Runtime project is invalid. Performing full download might solve the error.

Contact Customer Support.

The downloaded runtime project changes are rolled back. The previous version of the project in Runtime is used.

Loading aborted (errors: 1; warnings: 0).

Installed software

Totally Integrated Automation Portal - Version V20 Update 3
WinCC Unified - Version V20 Update 3
Runtime Manager (Unified Runtime version: V20 Upd2))

Need advice

Yes. Problem is the same even in a new blank project with a hmi with only one screen with no content.

Hello, I also had a similar situation.

My simulation worked well on my desktop PC, but when I tried to run a simulation in my laptop, I got the same error.

I found that there is a solution in the FAQ by siemens support.

https://support.industry.siemens.com/cs/document/109775493/wincc-unified-error-when-loading-the-project-loading-will-not-performed-because-preconditions-are-not-met-?dti=0&lc=en-AU

I did what they say (canceled the encrypted transfer also in the WinCC Unified Configuration), and now the simulation works well.

Good Luck