How do I unencrypt one particular form?

Hi had turned the encryption on and then off. In that time I received one encrypted form and there is no pop-up to upload my key (I do not know where to find my key either)

Please help!

 Unfortunately, the encryption keys are not stored in our servers, and there is no way to obtain the lost key. You may disable the encryption to receive new submissions without encryption; however, the old encrypted files will remain encrypted. You may generate a new key by enabling encryption again, as our guide indicates.

For rest of the guide, please visit Encrypted Forms and How to Use Them.

You need to upload the key file to Form's Submissions page for the only first for each browser, as I demonstrated the process for you in below GIF.

If you have further questions, please don't hesitate to ask us.