Please don't use bug reports to request help with configuration problems. There are very few people who read the bug reports, and many more who read the Jenkins users mailing list.
Please ask questions like this on the mailing list so that more people than the plugin maintainer can assist with the answer.
In this case, you probably don't have the location of your git program configured correctly.
You may also want to consider placing your Jenkins HOME directory in a path which does not include spaces. There are a number of programs and plugins which may struggle with spaces in the path to the Jenkins home directory.