How can I recover traffic after incorrect URL redirects in site migration?

Hi, I recently discovered that when migrating my site from wix to shopify about 6 months ago url redirects were not put in place correctly resulting in a large loss of traffic to this day. I have done some research on the subject and was wondering if anyone else had any knowledge to whether there is anything that can be done at this point to help recover any of that lost traffic or to have the site better setup for the crawlers. Thanks