How do I add 'leave a message for the seller' on every product? (Every product can be customized on my store so it'd be nice to have a box coinciding with each item instead of having customers list information at checkout.)
Also, right now I can't access customize checkout because apparently, something is missing in the system?
I'm using Boundless Theme.
Karlie here from the Shopify Support Team! Your best option here would be to use an app that would allow you to include a customizable text box on your product page. These apps are technically used for offering different product options, but you could totally use the text box input option on these apps to include a 'leave a message for the seller' box.
The apps I would recommend checking out are;
Can you tell me more about what's happening when you try to adjust your checkout? What are you trying to customize on your checkout page? Any details would be helpful when troubleshooting.
Looking forward to hearing back from you!