Good point from Eric, if you have identified that there is a penalty then you can have it removed, and then 301 the old domain (or go on with the old one).
Let us know more about the penalty and we can help you to remove it. I suppose it´s based on links (most common).
- Look for messages (and Manual actions) in Google Search Console
- Use Open Site Explorer (https://moz.com/researchtools/ose/) to identify low quality links and remove them.
If there are some links you cant remove, you can tell Google to ignore them by using their Disavow-tool.
You find the tool here: https://www.google.com/webmasters/tools/disavow-links-main
Good luck!
