Due to some changes in the Google File Picker API, the forms library has to be updated.
Here's a step by step guide that explains how you can update the library for your forms.
After you have updated the form library and redeployed the app with a new version, go back to the Google Sheet, open the Form editor, and save it again. This is required to clear the old cache.
If you have any questions, please post in the comment thread.