I'm receiving encrypted form responses that I cannot decipher

If it has been many days since I changed my encryption key, why am I receiving encrypted form responses that I cannot decipher.

As noted above, I have had to change my key several times because of form wonkiness. The last time was last week, and I have received a couple of submissions since that time with no problem. However, I received one last evening that was encrypted and unable to be viewed. Is this because someone had a cached version of an old form with an old encryption key, and sent that in? 

No, users should be able to see the new version of the form and you can use the new key to decrypt the data. But when you do, does the data remains encrypted or just part of it? We need to know this so if needed, we can submit it to our developers. 

My apologies for my last statement about the old key. I need to confirm it to our developers if that is still the case for the old key. I'll let you know.

All of the data is encrypted on the form received, not just part of it. I haven't yet tried to open it using old keys (clearing the cache, choosing the old key when prompted, and then opening), but I had this happen to me before (when I had to unencrypt a form, and reencrypt), and I was never able to open those, even with all of the keys I had. Strange. 

I meant to ask whether the data is completely shown after providing your key or just part of it. We have some reports like this before that after providing the key to decrypt, the whole data is not showing up, some fields remain encrypted.

Clearing your browser cache, cookies, and other preferences won't help. The key is not dependent on these things in your browser.  You can find more details about the encryption on this guide: 

https://www.jotform.com/help/344-What-are-Encrypted-Forms-and-how-to-use-them-as-expert 

But I would also suggest trying to open up the submissions using another browser. Check if that works.