I encrypted my data and have my private key saved on my computer. However, when I go to download the data from the forms it remains encrypted.

Similarly, the data the automatically connects to my google sheets is transferred as encrypted data. Therefore, I can't download all of the data together in one file without it being encrypted. Previously the website asked for my private key and that took care of it. However, after losing that key, I had to use another key for encryption, and since then, it hasn't prompted me to put in the new key. 

Unfortunately, it is not possible to download decrypted data from encrypted forms. It is also not possible to send decrypted data to Google spreadsheet. Some of the features that are not available for Encrypted Forms* are:

1. PDF Downloads,

2. Reports (this includes downloading Excel and CSV files from within Submission Panel),

3. Emails that contain form data in them.

* All server side gathered and processed data can only be retrieved in encrypted form because your private key is never sent to our servers

If you lost your key then your data is also lost. With the new key you will be able to decrypt only submissions that you received after you created new key. You can try to find your original key in downloads folder on your computer. 

If you are not prompted to upload key on submission page of your form, please try to use some other browser or try in incognito mode. 

More about encrypted form you can find inside of this guide:

Encrypted Forms and How to Use Them

Let us know if you need further assistance.