I’m absolutely perplexed on this one and its driving me nuts ! Under “Sales Channels” on the dashboard and selecting “Google and You Tube” it takes me through to the next screen where I can select “Manage Products” - this takes me through to the bulk edit screen. The issue is I have to keep manually changing all my products under “Custom product” to “False” because Shopify keeps changing them back to “True”. None of my products are custom, they are all purchased through suppliers with barcodes and these are entered in the correct field. This means this field should be false. Why does it keep changing it back and what impact does it have on my SEO, it’s driving me nuts as I have to manually do this to over 1000 items at least every few weeks.
Why I can not answer, but I can guide you to consider contacting support to report your technical issues here: https://support.google.com/merchants/contact/shopify_3p_support_app
Alternatively consider a more advanced tool such as: https://apps.shopify.com/multiple-google-shopping-feeds?show_store_picker=1