SOLVED - Need help with a migration problem to a new Mac: header images not visible

I have migrated RW 7.2.2 and adding from my old MacBook to a new iMac recently.

When I open my project on the new Mac the header image is not shown in preview (Mirage theme). But when I look into the folder with the editable images, then all the images are there.

Now I took this project and opened it on my MacBook with RW 7.2.2 - it is baffling that the header image is visible.

Who can help me with completing my migration process? Which folder do I need to transfer again from where to where?