i have a problem with the Feed when i choose Content API in the Google Merchant Center in all my Shopify's Accounts. its didn't show me the products at all.
Aside from your issue, be warned, having multiple websites puts you in high risk of getting suspended. The general rule is 1 business = 1 website. Unless you have a unique business entity.
If you can't list your products, then most likely you are missing a policy.
If you provide more details of your issue, such as which data feed app are you using.
Screenshots of your issues, then we can try and guide you.
You need to use an app, here is a list: https://apps.shopify.com/search?q=google%20shopping