Whenever i generate a rig a character using rigify and generate it, the generated rig works fine but when i rig and generate the another model in the same file. The selected rig does not generates but the first one does. How to solve this problem. Help will be appreciated.
After you generate a rig, rename it. The armature generated is given the name
rig, when you click generate on the second metarig the first rig is updated because of it's name.
This only applies up until 2.78, the about to be released blender 2.79 includes an updated rigify addon that makes this easier. The new version has options to overwrite or create a new rig, as well as choosing which rig to overwrite.