Your mesh is made by different spare parts, which also intersect each other, and this is not what automatic weight is ready to manage.
A workaround can be separating every single piece in one different object (Jacket, legs, pants, ect.), you can do it by selecting all vertices, then press P > Separate by loose parts.
Then you can parent every object to the rig, and later you can join (Ctrl + J) everything in a single mesh as weights are properties of vertices, and they don't change if the meshes are merged.
Anyway I would suggest you to parent your mesh using With empty groups option, then do manual weighting, with paint or direct assign, because with automatic option you will have lots of intersections between various parts of the mesh (and possibly clean some ugly topology and eliminate interiors as far as you can).