Splunk Add-on for Salesforce throws 500 Error

[axavierequinix]

I am using the Splunk Cloud instance.
I was able to successfully install and configure the "Splunk Add-on for Salesforce"
But, Splunk Add-on for Salesforce is not pulling any data from Salesforce, but see the following in the log.

The response status=500 for request which url=https://login.salesforce.com/services/Soap/u/39.0/ and method=POST.

Any idea?
I'm not seeing any history in salesforce for the configured user.

[jawaharas]

In my case, the error was due to expired user credential.

[gordo32]

So far, I've run into 3 things that can cause 5xx failures:
1. You have an ampersand (or other non-allowed character) in your password. As a test, use just upper/lower/alphanumeric to make sure you get the add-on working, then you can play with which characters are or aren't allowed (I haven't done an exhausting test)
2. The account you're using doesn't have API access assigned to it in Salesforce
3. You don't have a token specified OR your source IP isn't whitelisted in Salesforce

Hope these help everyone...