Thanks RutaGanusauskaite RutaGanusauskaite for the information. I've read the entire thread and followed the instruction precisely, however, whenever I send a test order confirmation email or look at the preview, the "View your order" button always leads to https://checkout.shopify.com/xxxxxxxx/orders/123456abcd/authenticate?key=abcdefg
with the following message:
"The checkout page you’re looking for does not exist
The URL you entered may be expired, deleted, or invalid.
Return to the home page to continue shopping.
Return to home page"
Note: xxxxxx was originally a set of numbers in the URL, I just changed it.
What am I doing wrong, and how do I fix this? Please let me know.
Thanks in advance.