Google Forms upload errors and the fixes that work

When a Google Forms upload fails, the cause is almost never a mystery. It is one of two named errors, and each one says exactly what is wrong if you read it as a set of conditions instead of an insult. The first error lives on the question: Upload 1 supported file. The second lives on the form: the banner about the folder containing responses being missing. Both stop responses from arriving, and the second one stops the whole form until you fix it.

Error 1: "Upload 1 supported file"

This is not a complaint about your file. It is the question's rule stated out loud. The form owner set a maximum of one file per answer, possibly restricted the allowed types, and picked a per-file size tier. Respondents see the summary as a single line under the question, conventionally written as Upload 1 supported file. Maximum size ….

When the upload will not go through, check in this order:

• Count matches. The question allows exactly one file, so two attachments — even two pages of one PDF scanned separately — are rejects. Combine or compress first.
• Type matches. If the owner ticked specific types, anything off the list fails no matter how small the file is.
• Size matches. Try the smallest tier that still fits: 1 MB, 10 MB, 100 MB, 1 GB, 10 GB per file.
• Account exists. Google Forms will not open the picker until the respondent signs in. A missing upload option entirely is a different failure; the disabled upload guide covers shared drives and admin rules at the form level.

If you are the owner, the fix is not telling people to "upload more smartly". Open the question and widen the rule: raise the maximum file count, add types, or move to a larger tier. The rule text updates for everyone the moment you save.

Error 2: the missing responses folder

The full banner reads:
The folder containing responses to file upload questions can't be found. This form won't resume collecting responses until the folder has been restored.
No formatting to parse, just a verdict. Google Forms stores every attachment in a folder it created in the form owner's Drive, usually named after the form. When that folder leaves reach — emptied into the bin, deleted without ceremony, or moved somewhere the form can no longer see — Google stops collecting rather than inventing a new destination and orphaning the old files. The banner is Google protecting data, and also announcing that your form is offline.

Restore path, in order of preference:

1. Open Google Drive's bin and search for the form's name. Restore the folder with everything inside it. Files return, collecting resumes, and the banner disappears on reload.
2. If the folder was permanently deleted or the bin was emptied, no restore exists. The attachments are gone; the banner stays until you delete the upload question and add a fresh one, which starts an empty destination with no history.
3. Workspaces on paid plans can ask their administrator to escalate to Google support. That is the only in-product route after permanent deletion, and its success rate is not guaranteed.

One prevention note worth more than every fix above: don't tidy the Drive folder the form uses, and don't reorganize it into a shared drive mid-collection. Google will not transfer the association for you.

Fastest fix for each upload error

A route without these walls

Thunder Forms sidesteps the first error by stating the rules on the question before anyone types: allowed types, the 12 MiB per-file cap, and a maximum of ten files per field, all visible up front. For the second, the destination is a folder you choose for each upload field, not one Google created silently — you always know which folder to leave alone, and files land there as ordinary Drive uploads. And the account wall never appears: respondents upload on a public link with no sign-in.

Honest ceiling, same as always: those files still live in a Drive folder, so the bin rules apply to you too. The difference is choice — you picked the folder, you know where files should be, and you preserve it with the same care as any folder that matters.