Why are abandoned carts not showing up in my new ecommerce platform?

Hello.. I switched my website from bigcommerce to shopify a few months ago and no traffic or sales on it since I switched.. I had a sales from my old website and also could see abandoned carts not one.. since I switched.. I have google anyaltics and i Can see on enhanced e commerce people adding to cart and getting to check out page.. but this not show up on my shopify account? I dont know what im doing wrong but would love some help with this.. i have placed orders on my desktop and mobile as test and there is no issue.. thankfully I do markets which keeps my sales going but the website is letting me down massively since switching over..

Dear ACOUSY42, Welcome to the Shopify community.

Shopify makes it simple to set up an online store and has several features that BigCommerce lacks. It is important to know which method was followed for the migration. Did you use a third-party app or did it manually by Store Importer? Please provide your store URL so that the exact issue can be diagnosed.