The ACF Gallery Field disappeared when it is empty, only the add image button shows up and although it shows the media uploader, the field remains hidden and you are not able to see images. This only happens to the admins or any user role with the upload files capability
Upon checking field may have been affected by an acf-hidden css rule that loads via this file: webpack://advanced-custom-fields-pro/src/advanced-custom-fields-pro/assets/src/sass/_global.scss