Below is a list of errors most commonly encountered and what they mean:

Errors that MUST be fixed to avoid account suspension:
  1. Item requires a GTIN: This a Google unique identifier for every product. From January 2017 It will be compulsory to have a GTIN for all products being listed on Google Shopping. These must be supplied in the product feed that is sent to Cresco Data. 
  2. Images too small: Images have a minimum size requirement. Please see image requirements for Google Shopping. 
  3. Product Pages cannot be accessed: The product landing page cannot be accessed by Google. This could be for various reasons. For information on how to fix this see https://support.google.com/merchants/answer/6098155?hl=en
  4. Product Pages cannot be accessed by a mobile device: The product landing page cannot be accessed by a mobile device. For information on how to fix this see: https://support.google.com/merchants/answer/6098296?hl=en
  5. Product Pages cannot be crawled because of robots.txt restriction: Please update the robots.txt file on your web server to allow Google's crawler to fetch the provided landing pages. For information on how to do this see https://support.google.com/merchants/answer/6098185?hl=en
  6. Wait up to 3 days for image crawl to complete: This is for items that are pending to be shown in Google Shopping, because Google can take up to 3 days to fetch the images. 
  7. Automatic item disapprovals due to Policy violation: This only becomes a serious issue when a large percentage of products are affected.  may be an ingredient in a product, or a specific term that is against Google policy regulations so it filters them out. You can reach out to google support at https://support.google.com/merchants to chat to them about this and see if they can provide specifics so you can decide if anything can be changed in the product information.  
Warnings which could negatively impact the performance of your ads
  1. Invalid GTIN value: Some of your products may not have a GTIN associated with it for some reason. To resolve various issues with your product identifiers, see: https://support.google.com/merchants/answer/160161?hl=en 
  2. Low Image Quality: The main image associated with your item has poor image quality. 
  3. Invalid color name in attribute: color: The color associated with your item may have invalid syntax, or a number, or combined color names. For more Product data specifications see:  https://support.google.com/merchants/answer/7052112?hl=en&visit_id=1-636153739006781284-770988136&rd=1