A little problem with importing a poject from UE 4.25 to 4.26

Hello everyone!

How are you doing?

I started to learn Unreal during last spring I am now very exited in learning while building my project.

I have been browsing in the market place yesterday and found a nice asset I wanted to use. This asset being only compatible with UE 4.26, this was the occasion
to try the new engine.
I was surprised to see that I was proposed to use my project from 4.25, as I thaught projects made with an earlier version are not compatible…
Everything was migrated well, exept for only one texture in my landscape. The snow, an important one!
All texture I am using come from the exellent Procedural system. My snow layer has been replaced by the global ground layer. When I go inside my blue print,
nothing had been changed, the snow layer is where it should be with the correct texture. Even when I paint, it paints global ground instead of snow…

Can someone help me with this issue?

Thanks a lot.