401 Error, Mule while Username/Password are Correct - api

Question

I am trying to use postman to call an API that I have deployed with Mule. I have downloaded this API from a trusted source (Collibra) and thus expect it to be in working condition.
The API Request:
http://localhost:8081/connect/dgc/export/asset?filter=name%20STARTS_WITH%20E
Here is the Basic Auth setup in one of the xml files.
<mule-ss:security-manager name ="authenticationManager" doc:name="Spring Security Provider">
<mule-ss:delegate-security-provider
name="memory-provider" delegate-ref="authenticationManager-common" />
</mule-ss:security-manager>
<spring:beans>
<ss:authentication-manager alias="authenticationManager-common">
<ss:authentication-provider>
<ss:user-service id="userService">
<ss:user name="${service.user}" password="${service.password}"
authorities="ROLE_ADMIN" />
</ss:user-service>
</ss:authentication-provider>
</ss:authentication-manager>
</spring:beans>
And here is the setting of the username/password in a properties file.
service.user=user
service.password=password
The following error appears when I make a postman GET request with the correct credentials.
Failed to connect/reconnect: Work Descriptor. Root Exception was: Unexpected response with status code: 401 was returned. Message was: {"statusCode":401,"titleMessage":"Not authorized","userMessage":"The user name or password is wrong. Try again."}
And here is the error that appears if I use the incorrect credentials.
Root Exception stack trace:
org.springframework.security.authentication.BadCredentialsException: Bad credentials
What could be going wrong to have the error appear when I am passing the correct credentials through the Basic Auth? I have double-checked the string with an online header generator and it is indeed correct.

Answer 1

It is difficult to troubleshoot without understanding the API implementation, but given the error with incorrect credentials seems to come from the Spring Security Manager and with the correct credentials it looks to be connecting to something else, it is possible that the API is calling some backend system or API and failing to authenticate to it.