There are many hours of video showing the process to rig a range of characters from static mesh, engine samples, cc3, daz3d etc.
From what you describe I assume that weight paint did not transfer from your original armature to the final rig. Was your original character an existing rigify rig? If so you need to remove rigify. Then follow procedure shown in the videos to rename bones and the rest of the process. That should fix your issue.
You didn’t really provide much detail on what you did or how you got there so that is my guess on the matter.