Altium designer transfer to pcb issue

[giorgos3924]

Hello!
I designing a pcb with 14 sheets in hierarchical option. In order to transfer my components to pcb doc, after executing and try to validating i get error sign in some net names without error message! See image1.
With that error i get "Class already exist" error in my all sheets names and in all signal harnesses.

After ignoring the above issues, the second issue that i had encounter is in Engineering Change Order when i import the objects and executing, after it, in trying to import same objects again, without change anything in pcb or in schematic, some of the objects apears again and still remaining in Engineering Change Order, I don't see the expected "no differences detected" message. This disturbing me and im afraid for pcb design
See image2.

Note that my project, compiled successfully.

[T3sl4co1l]

Are your components being placed as well?  If you haven't set a valid footprint (including library path), you won't get components on the PCB, and therefore the nets connecting them.

It's not obvious if you have any parts with valid footprints...

Tim

[giorgos3924]

And what's the "Class already exist" error which i get?