Splunk Salesforce Add-On Oauth ERROR UiAuth - Request from 127.0.0.1 to "/en-US/splunkd/__raw/services/Splunk_TA_salesfo

[mfbma]

I have configured Oauth in a custom account in the splunk salesforce Add-On app.  After configuring the account and saving the configuration it reaches out to salesforce.  I login to salesforce and its states grant access.  Once I click submit it comes back with an error  

"Error occurred while trying to authenticate. Please try Again" in the app. 

I am not sure what the issue is or if this is a need to configure something on the salesforce side. 

[n7_guru]

Any luck with this? Same scenario. Configured Splunk Add-on for Salesforce v 4.1.0 (we run Splunk 7.3.3 on-prem still). I've configured oauth settings with client_id, client_secret and add redirect url to Salesforce app I made. I get pop-up to Allow or Deny access which I approve and then get...

"Error occurred while trying to authenticate. Please try Again."

Doesnt even point to a log file to look a what is causing issue. I can configure with basic auth and that works but Id prefer to oauth.