There are many causes of warnings or errors in your feed. We have compiled some common errors on Google Merchant Center and Facebook catalog.
I hope the instructions in this article will help you

Google Feed

Unclaimed website
Account isn't eligible for enhanced listings on surfaces across Google
Missing value (shipping)
Processing failed (image link)
Missing value (image link)
Images too small
Promotional overlay on image (image link)
Invalid image
Generic image
Limited performance due to missing identifiers (gtin, mpn, brand)
Invalid value (gtin)
Unsupported value (restricted) (gtin)
Ambiguous value (gtin)
Insufficient product identifiers: missing two out of three attributes (gtin, brand, mpn)
Missing value (gtin)
Missing value (size)
Missing value (color)
Missing value (gender)
Missing value (age group)
Unavailable Mobile Landing Page/ Unavailable Desktop Landing Page
Mismatched Value (Price) (Page Crawl)
Mismatched Domains (Link)
Invalid sale price

Facebook feed

Image_link a required field is missing
Products can't be added by multiple data feeds: ids
Property rich_text_description contains invalid HTML
Title too long
Uppercase tittle
Products have Pending status for too long
The permission for our app has been removed on Facebook
The data source has been deleted on Facebook Catalog
Can't reconnect Facebook feed after reconnecting several times
Brand:gtin:identifier_exists:mpn universal ids are missing