Sentry splunk integration

worker_1                                    | 17:32:07 [INFO] sentry.plugins.client: plugin.http_response (plugin='splunk' status_string='connection_error' error="SafeHTTPConnectionPool(host=app01-splunk-', port=8088): Max retries exceeded with url: /services/collector (Caused by NewConnectionError('< object at 0x7f8b2c8d6128>: Failed to establish")
worker_1                                    | 17:32:07 [INFO] sentry_plugins.splunk.plugin: integrations.splunk.forward-event.error (instance='http://app01-splunk:8088/services/collector' project_id=6 organization_id=1 error='Unable to reach host:')

On a new upgraded Sentry , getting this when integrating with splunk. Anyone faced this.
Not clear why the issue is reporting. Connectivity is fine , curl to the event collector with token works,

Does the token need to be defined in or just the UI should be ok?