Only trigger convertkit_api_access_token_invalid when an invalid access token is used

Otherwise a 401 for e.g. member content will result in the access token wrongly being removed, when it’s a valid access token.

Author: n7studios

src/class-convertkit-api-v4.php

@@ -1475,7 +1475,7 @@ public function request( $endpoint, $method = 'get', $params = array(), $retry_i
 							// Attempt the request again, now we have a new access token.
 							return $this->request( $endpoint, $method, $params, false );
 
-						default:
+						case 'The access token is invalid':
 							$error = new WP_Error(
 								'convertkit_api_error',
 								$error,
@@ -1494,6 +1494,13 @@ public function request( $endpoint, $method = 'get', $params = array(), $retry_i
 
 							// Return error.
 							return $error;
+
+						default:
+							return new WP_Error(
+								'convertkit_api_error',
+								$error,
+								$http_response_code
+							);
 					}
 
 				case 429: