If the feed rules tab is not available, then you must have added the products manually, in this case rules do not exist.
Rules can be applied if you are using content API, google sheets, scheduled fetc.
If you continue to struggle, contact Google Merchant Center support directly or if you like you can contact me to help you personally.
As it seems like you created your own feed, here is a guide: https://support.google.com/merchants/answer/6324478
Yes I enter every product one at a time. At that time I did not know about the csv file import. I still don't know how to use it, but I know it is possible. In Shopify I didn't have the three dots to import the csv file.
Anyway do you have any ideas on how to eliminate the "Barcode Invalid" error? I believe I received the error when there wasn't a barcode on any product. I fix this I installed the Shopify App Retail Barcode. It automatically put barcodes on every product. The message "Barcode Invalid" then came up on every product.
I would appreciate any help.
You can not use self generated bar codes. Only official GS1 international barcodes are approved. If the manufacturer has not assigned bar codes. Remove brand, mpn, gtin and set identifier exists to no.
If you do not know how to achieve this, get in touch with your data feed app support team.
If you think they are official and you paid for the bar codes, as they cost around $25 per bar code. Then simply submit the bar codes. However please remember that submitting invalid data is a policy violation.