Unable to add materials in mesh editor

Not having any luck on the other unreal forum so thought I’d try my luck here. Title pretty much says it all. I can’t add any materials to assets in the mesh editor so that when I drag them into a level they already have their set material. Process is-

  1. I’ll double click on a mesh in the content browser or from the details panel of one thats already in the level which opens the mesh editor window I think its called.
  2. Ill click and drag a material from the content browser that is already applied to dozens of assets in the level
  3. hover it over the material slot of the asset in the mesh editor and a green dashed box surrounds the material slot
  4. I release the LMB and nothing happens, the material thats already there remains. E.g- world grid material or one that was applied before this starting happening.
  5. Also unable to click on the drop down menu to choose a material.

Some pics of the material slots, one with materials in them from before this started happening and one with a new mesh that I imported after it started happening. Thanks for reading.

295246-screenshot-4.png

295247-screenshot-5.png

Cloning the project fixed this.