Hi, when I assign a new material of my rigged mesh, the mesh connection is lost. Do you know why?
Hello and welcome to the forum!
No idea why a new material assigned to a mesh is messing up the rigging of the mesh, that shouldn’t happen. Check that the mesh still has vertex groups named for the bones and that it has an armature modifier, (the 2 basic things need for deforming a mesh with an armature).
If that checks out, upload the .blend file with instructions on how to make this happen.
Since you are new around here, you probably can’t attach the file to a post, so upload to a file sharing site and post the link to the file.
Randy