This has been an issue for me since Gutenberg came out. The preview only shows blocks, and does not show any of the custom fields at all. I thought this was a WP issue, but it seems to be an ACF issue, as disabling the gutenberg editor enables the preview.
I’ve been coding my new sites fine with 5.8, using blocks for everything, and they show up just fine…but for older sites that were designed pre-gutenberg, I am having this issue.
I’m not finding any solutions on this, please help me out! Thanks!