On my pre-production environment, I am getting an error when trying to create a new User.

We do not have Data Encryption enabled on pre-production, so I'm not sure where the encrypted fields are. I have tried many things to resolve it, the most promising being running these commands on our pre-production DB:
UPDATE EmailServerProfile SET IncomingPassword=null
UPDATE EmailServerProfile SET OutgoingPassword=null
UPDATE Mailbox SET Password=null
UPDATE Queue SET EmailPassword=null
UPDATE UserSettings SET EmailPassword=null
This has seemed to work for many people on various forums, but while it did clear the present data, I am still unable to create a New User. If I DL the log file of the error, this is what it contains:
Unhandled Exception: System.ServiceModel.FaultException`1[[Microsoft.Xrm.Sdk.OrganizationServiceFault, Microsoft.Xrm.Sdk, Version=8.0.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35]]: Cannot open Sql Encryption Symmetric Key because Symmetric Key password does not exist in Config DB.Detail:
<OrganizationServiceFault xmlns:i="www.w3.org/.../XMLSchema-instance" xmlns="schemas.microsoft.com/.../Contracts">
<ActivityId>9ec8de5c-722a-4f21-b06f-30731b939d93</ActivityId>
<ErrorCode>-2147187410</ErrorCode>
<ErrorDetails xmlns:d2p1="schemas.datacontract.org/.../System.Collections.Generic" />
<Message>Cannot open Sql Encryption Symmetric Key because Symmetric Key password does not exist in Config DB.</Message>
<Timestamp>2018-03-13T18:23:29.9071551Z</Timestamp>
<ExceptionRetriable>false</ExceptionRetriable>
<ExceptionSource i:nil="true" />
<InnerFault i:nil="true" />
<OriginalException i:nil="true" />
<TraceText i:nil="true" />
</OrganizationServiceFault>
I can see in the Data Management Settings that Data Encryption is not enabled, but I don't want to enable it if I don't have to. I've been able to create new Users on our pre-production environment before, but it's been a couple of months since I had to so this is the first time I've encountered this error and I'm not quite sure what may have changed on our end in the meantime. I am able to successfully create new Users on our production environment with no issues. I tried to see if Data Encryption was enabled on the Production site, but I got that SSL error that prevents you from seeing the window:

The thing is, I don't want to Disable the SSL check on the Production DB just to see this window, since everything is working properly there currently.
So, after I apologize in advance if I've left out any helpful information, I'm asking if anyone has encountered this before when trying to add new Users, and can offer any suggestions on how to resolve it.
Thank you in advance for any help you may be able to offer.