Key field with initial value UNIQUEID() not filled in when I add a row using Google Forms

[nhcohen]

I have a table whose source spreadsheet has rows added to it when a Google Form is submitted. This works, but I wanted to replace a row-number key with a unique key, so I performed the following steps:

1. Add a new column internal case ID to the source spreadsheet.
2. Manually cut and paste UNIQUEID() values in the internal case ID column of the existing rows, as described here.
3. Click "Regenerate Structure", which adds the column to the columns view of the editor.
4. In the columns view, remove the checkmark from the KEY column of _RowNumber and set the attributes of the internal case ID column as follows:
   TYPE Text
   KEY? ☑
   LABEL? ☐
   FORMULA =_____
   SHOW? ☐
   EDITABLE? ☑
   REQUIRE? ☑
   INITIAL VALUE =UNIQUEID()
   DISPLAY NAME =_____
   DESCRIPTION =_____
   SEARCH? ☐
   SCAN? ☐
   NFC? ☐
   PII? ☐
5. Save the changes.

When I submitted a form from Google Forms, a row was added to the spreadsheet in which all cells other than the internal case ID were filled in, but the internal case ID remained empty.

I noticed that row 1 of the spreadsheet had a comment of the form AppSheet:{...} in each column except the internal case ID column. I closed the AppSheet editor, went back to the AppSheet add-on in Google Forms, and clicked PREPARE and LAUNCH. The AppSheet editor reopened and the internal case ID column of row 1 in the spreadsheet now had the following comment:

AppSheet:{"IsRequired":true,"IsEditable":true,"Type":"DateTime","IsKey":true,"IsHidden":true}

I corrected the type from DateTime to Text.

None of this helped. When I submit a form from Google Forms, a row is still added to the spreadsheet in which all cells other than the internal case ID are filled in, but the internal case ID remains empty. What can I do to populate the key?