Hi there
I would make sure you take a look through this migration guide from Moz as it has steps to ensure your site is properly migrated.
From there, I would check the following:
Sitemap
Internal Links
Canonical Tags Change of Address Tool (if necessary)
The first three links above could potentially be utilizing old URL structures, so you want to make sure that you change those and they are up to date. The last is for if you changed your domain at all.
Your analytics tag should not be the reason that your new URLs are not appearing in search.
After these steps, I would then go through a backlink audit and make sure that you update any quality backlinks or listings and remove and/or disavow any links that you find to be spammy or irrelevant to your website.
Hope this helps! Good luck!