1) If your store is using a password page on its storefront: (https://help.shopify.com/en/manual/using-themes/password-page), then Cross Sell is restricted in its ability to search your shop's products by 2500 items.
If your store has more than 2500+ items and you wish to assign cross sells, you'll have 3 options:
- De-activate your storefront password while assigning cross sells.
- Use an app like Locksmith to password protect your store (while it's in development) instead of Shopify's password page
- Request a Bulk Upload and send it to us for bulk uploading.
2) If you are not using a storefront password and are having issues searching for items in Advanced or Quicksearch modes, please read about how search works in Cross Sell to understand its limitations: https://help.csell.co/a/solutions/articles/106281