Google, Printful, and the brand/MPN/GTIN

So this is driving me nuts.  

Google Merchant Center says many of my products are not being shown on Google because they don't have a GTIN or MPN.  I am using Printful to make the products and Printful says that Google's own help website says that for custom made products (like their print on demand products) you don't have to have a GTIN or MPN.  

On Google's website, I have repeatedly added the Brand (Amber Live) to the products, and they say it's fixed for a few minutes and then it reappears with the exact same issue saying that they need a MPN.  I chatted online with someone at Google Merchant Center who told me I would have to get a letter on letterhead from Printful that listed each product and said that it doesnt have an MPN in order to get an exception.  AND then any time I added new products I would have to get a new letter listing those products.  In addition to that, when I chatted with someone at Printful, they said they won't provide letters like that and they repeated that Google doesnt require a MPN for their products because they are custom printed. 

Has anyone else had this issue, and how did you fix it?  When I chatted with someone at Squarespace today, they basically said these are two third parties, and they could only help with initial integration.  After that it was up to me.

Thus, no one has actually been helpful.  Has anyone experienced this and found a solution?  Google is the largest search engine out there, and it's insane that I can't get my products listed on it.

THANK YOU for your help.

Thank you!  Just what I was looking for.

That fix suggestion doesn't get suggested for me unfortunately. I don't even get the MPN suggestion - which I did do for a hot second but that's disappeared now as well. Google Merchant Centre is a complete nightmare, it's honestly one of the worst things I've ever used. I ended up having to edit things from the product edit page, which does at least let you edit everything at once, but it's laborious to have to jump in and out of the edit page for every product, and once you've finished editing it throws you back to the start of your product list, rather than where you left off, meaning endless scrolling and trying to remember where you got to. I tried using the filters but they are pretty garbage as well. Sorry - ranting...

Anyway, if anyone else has this problem, there's nothing to stop you assigning your own MPN for items, as since they are your own designs, you could have your own MPN for them per design. This is what I've been using as we sell items that we've designed ourselves, so we just make up an MPN.

For anyone outside the USA, it's worth noting that the Squarespace GMC integration assumes you are in the US so your feed is assigned as "US" whether you are in the US or not... which I only found out by trying to use it and then contacting Squarespace support to ask how I get the feed assigned to "UK" rather than "US". But that's not a thing you can do apparently, and the reply I got was "I can see how that would be useful". Ha ha. Yes, Squarespace, the rest of the world exists. If anyone knows if this has been changed and now supports UK feeds correctly - please let me know!