You follow its given instruction, yet it still cannot work, then this is what you should do:
1. Go to this link: https://developers.google.com/+/web/badge/
2. There you can create a Badge or an Icon.
3. Firstly, you paste your Google Plus URL.
4. After you have made your selection and adjustment, you can see a box of code on the right hand corner below.
5. Copy the code and paste it as a widget on your blog.