September 13th, 2022
GitHub can be used to sync Shopify themes and attempt to move over a theme from a development store to a live store.
Sometimes this will result in a 404 page but just on one specific page such as the product page.
I was using Dawn as my base theme and ran into this issue and it appears there were others as well.
None of the solutions offered worked for me but the following allowed me to debug the error:
Under your theme in the admin panel, select “View Logs”.
Add any missing metafields from the error log.
For me, I had missed copying over one single metafield which apparently is enough to break just the product page and cause a 404.
Shopify should definitely consider adding error output or something to show this in the future.
If you don’t use GitHub you may not be able to see these error messages.