Shipping issue from multiple Printify printers

[evolve555]

On my store I sell a variety of items fulfilled by Printify. I sell shirts printed by SwiftPOD, Mugs printed by MyLocker, Poster Prints printed by Circle Graphics and stickers printed by SPOKE, all within the Printify app.

So, I am able to fulfill the shirts and stickers just fine, but when I add the Mugs and Poster Prints, when I finally go to check out I get the error "This order can’t be shipped to your location. Contact the store for more information." followed by "There are no shipping methods available for your cart or address". I tried multiple addresses in multiple countries and got the same error. It only affects the mugs from MyLocker and the Poster Prints from Circle Graphics. Everything else generated through Printify adds and ships just fine worldwide. I've tried everything I can think of... Any advice???

[evolve555]

If it matters, I also have Printful to fulfill different items I couldn't find on Printify. Printful seems to take over a whole lot of things in Shopify, so maybe there's some kind of conflict, since printful does sell prints and mugs, which are the 2 items i'm having problems with.