How can I resolve the missing GTIN or MPN issue on Google Channel?

[roundabout]

Hey Guys,

I am not sure how far you got with this issue, but it's still around on my side.. 

As we manufacture all of our products by ourselves we do have GTIN number, nevertheless i tried to push the feed via google channel without GTIN reference (custom product ticked) and with it. Both did not work out and still shows the same message. 

strangely is does not apply to all of our products.... 

I found this thread, but it does not seem to be a solution available, without GOOGLE DEVS in place ???? 

https://community.shopify.com/c/shopify-apps/bug-report-identifier-exists-needs-to-be-set-to-false-f...

Can anybody help me to understand the solution or share how it's done the easiest way ? 

Your help is highly appreciated.