I'm facing similar problems:

I have a project with a few CPUs.

In Step7 V5.6 erverythings fine. And I did already perform "Save as" with reorganization.
I have also checked all CPUs / their S7 program folders.
All are set to "CPU-oriented unique message numbers.

But when I open with Step 7 V5.7 HF2 the projects  opens "read only" and claims about missing software package "SIMATIC STEP 7 Project Messages".

I do not have this additional PM package and I guess it should not be required in my case.

Any ideas how to solve this? 

Thanks

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Split from Step 7 Professional 2021 / 5.7 tragedy.

Hi,

You say that you 'have a project with a few CPUs'  do you have any other additional systems integrated withing your project (ie. HMI's, Drives etc)?

If so you may need to upgrade these systems as well.

See Siemens Forum: Entry type:FAQEntry ID:109780478, Entry date:07/22/2020

How do you open an integrated project (SIMATIC Manager) in WinCC V7.5?

Hope this helps.

The project also contains many HMI panels - programmed with WinCC flexible 2008 and integrated.
I have updated all of them with WinCC flex 2008 SP5 Upd2 before reorganization to have a new version here.

Drives are not integrated.

We are normally not using the "big" WinCC (e.g. V7.5) - so I have no experience how to open an integrated S7 project with WInCC 7.5 (your proposal pointing to https://support.industry.siemens.com/cs/de/en/view/109780478 )

My key question is: Why requires my project the PM packages when I did not configure it and is there any other option to get rid of this when reorganization dose not help.

I now installed S7-PM V5.7 (download from https://support.industry.siemens.com/cs/gb/en/view/109798411 )

Now I got rid of my problem! 
Result: Even without finding any use of the S7-Project Message in my project I was urged to install it to be able to work with Step 7 V5.7.

Strange, but at least I have a solution now.

Hi,

The only other thing I can suggest is to revert back to the original copy of your project and confirm which software packages are needed for your particular project. (Help -> About -> installed software - Display)

If this PM package is still being shown as a requirement, then some other package must have been installed at sometime (ie. RFID, Starter software). These packages need to be updated and added as well.