missing materials after rename

I renamed all the materials in my project and placed them in a newly created folder.
I made sure to run then when I closed the project and re-opened it again I got more than a 1000 error messages saying “Failed to load”

Any ideas on how to fix this?

Did you rename them in the content browser or in outside of Unreal?

Yes in the content browser.

I can’t believe how restarted Unreal can be sometimes.
In Unity, you can rename and move assets in anyway you like, all the remapping is done behind the scenes.
In Unreal it’s like working in MS Dos, if you rename or move a mesh, material or a texture from one folder to another it’s the end of the world.
Fixing up re directors (which is a pathetic feature in itself) only works half of the time.