Not Authorized or Problem Logging In Error When Saving External Data Source Configuration

If saving the external data source configuration shows one of the errors "Not authorized" or "Problem Logging In - No_Oauth_State: State was not sent back", follow these steps:

Ensure that the connected app domain is the right domain of the Salesforce organization.
Open Salesforce setup.
Open the authentication providers configuration.
Click the name of the Anypoint Platform authentication provider and ensure that it has these settings from the correct connected app in Anypoint Platform:
1. Ensure that the consumer key and consumer secret match the connected app in Anypoint Platform.
2. Ensure that the authorize endpoint URL, token endpoint URL, and default scopes are configured as described in Manual Setup.
3. Ensure that the test-only initialization URL, OAuth-only initialization URL, callback URL, and single logout URL match the correct domain of your Salesforce organization.
4. Ensure that your connected app in Anypoint Platform has the same domain as your Salesforce organization in its redirect_uri setting, a client ID and client secret that match those in Salesforce, and correct scopes.

To view details of the connected app, examine the UI or make this API call:

curl -X GET 'https://anypoint.mulesoft.com/accounts/api/connectedApplications/' \
   -H "Content-Type: application/json" \
   -H "authorization: bearer XXXXXXXXX"

This call returns a response like this:

{
"client_id": "5fafXXXXXXXXXXXXXXXXXXXXXXXX29c9",
"client_secret": "9509XXXXXXXXXXXXXXXXXXXXXXXXC10E",
"client_name": "ACM Integration Client",
"redirect_uris": [
  "https://YourOrgDomain.my.salesforce.com/services/authcallback/Anypoint"
],
"grant_types": [
  "authorization_code",
  "refresh_token"
],
"public_keys": [],
"scopes": [
  "offline_access",
  "full"
],
"enabled": true,
"owner_org_id": "f377XXXX-XXXX-XXXX-XXXX-XXXXXXXX9d08",
"as_id": "anypoint"
}

"YourOrgDomain" is replaced by your organization domain.