That is a know issue. A quick fix is to make an edit to all the products. This forces a push to send data to Google Merchant Center.
The issue is that Shopify only sends data when there is a change.
Compared to my application it lets Google collect data on a daily basis, and thus extends the 30 days, every day. Essentially it will never expire.
Hope this helps.
The key to avoiding issues, is to make sure you keep the same product id. This to avoid loss of data in Google Ads and also to avoid policy violations in Google Merchant Center.
For example in my application, you can use the default Shopify ID, or your SKU.
When you subscribe to my application, I set everything up to ensure zero down time. Simply contact me and I am happy to help.
I have tried that. I added a new attribute to every one of my items yesterday. I also added a new tag then removed that tag. I want to reiterate that on July 5 I was in google shopping. On July 6 I received the email and since then I have not been eligible for enhanced listings and am now not in google shopping.
I don't have SKUs but I have set the identifier to "No" and did so successfully.
Ah, thanks for the further info. Enhanced Listings and Google Shopping Ads are completely different and have different requirements.
I have a great tutorial on this which should help you: https://feedarmy.com/kb/requirements-for-enhanced-listings-on-surfaces-across-google/
The key issue most merchants have is the trust factor, which is something you will need to work on.
Pleasure, if you need any further guidance, you can ask here, Google's official community or you can contact me.