Troubleshooting
Each heading is something you might see. Start with the entry's notes and the codes in Failure diagnostics.
A notification was not sent
Open the entry. A note from Additional attachments names the notification and the reason, and ends with a code. Failure diagnostics explains each code and its fix. Fix the cause, then resend the notification from the entry.
If there is no such note, the plugin did not hold the notification back. Check Gravity Forms' own notes on the entry and your mail plugin's log.
"The entry has no source page" (source_missing)
The form was not sent from a single page. Gravity Forms saves the page being viewed when the form is sent, and archives, search results, a home page showing your latest posts and previews have none. Put the form on the page that holds the files. A form in a popup counts as sent from the page the popup opens on, so a popup on an archive has no page either. An entry made by code, for example through the Gravity Forms API, has no page either unless the code gives it one.
"does not show the Email attachments box" (record_type_disallowed)
The page the form was sent from is a post type that is not ticked under Show the Email attachments box on. Tick the type on the Additional attachments tab under Forms, Settings and save, then resend.
"has no files in its Email attachments box" (box_empty)
Edit the page the entry names, press Add files in its Email attachments box, pick at least one file and update the page. Then resend the notification from the entry. A page's list also empties when its last file is deleted from the Media Library.
The Email attachments box is missing from a page
The box shows only on the post types ticked on the Additional attachments tab under Forms, Settings. In the block editor it is a panel in the Post or Page tab of the sidebar. For a post type that does not support custom fields, it appears in the area below the content instead.
The notification is held back after importing a form
The settings were saved on another site. Open the notification. A red notice at the top of the Additional attachments section says so. Check each file, then press Update Notification. Attachment IDs differ between sites, so choose the files again if needed.
The email is held back as too large (size_exceeded)
One email never carries more than 25 MiB of files. The total counts every file in the final email, including files visitors upload and files other plugins add. Attach fewer or smaller files, for example by splitting a page's files across two pages. There is no setting for the ceiling. A developer can change it with the dagf_max_total_bytes filter. Your mail provider may accept less than 25 MiB anyway.
A file stored in the cloud is refused (storage_unsupported)
This version attaches files stored on your own server only. Files kept only in cloud or offloaded storage are refused. Keep a local copy of the file in the uploads folder, or choose another file.
The email arrived without the file
The plugin never sends a notification with one of its files missing, so check whether the file was one of its own. Turn on logging for PlugUpp Dynamic Attachments for Gravity Forms under Forms, Settings, Logging and send again. If the log says "attachment prepared" with the file listed, the email left your site with it, and your mail provider or the recipient's mail system removed it. Some providers block certain file types or large attachments.
Static attachments will not save
With Static attachments on, at least one file is needed. Press Add files and pick one, or turn Static attachments off, then press Update Notification again.
Notifications were sent without files while the plugin was off
While the plugin is inactive it cannot hold anything back, and Gravity Forms sends the notification without these files. Before you deactivate or delete the plugin, turn the affected notifications off or change them.
A private file will not upload
The message under Select files in the Private files tab says why. WordPress checks private files exactly as Media Library uploads, so a type the Media Library refuses is refused here, and so is a file over your server's upload limit. If the message says the file could not be saved in the private files folder, ask your host to check that the uploads folder can be written to.
View says I am not allowed
View works for signed-in users who can upload files. The link also expires with your session, so reload the page and press View again.
A private file shows an icon instead of a preview
The server could not make a preview when the file was uploaded. For PDFs that needs ImageMagick with Ghostscript, as for PDFs in the Media Library. The file is sent the same either way.