# Troubleshooting Contacts API error responses

This topic lists all the possible error responses you might encounter while using the Contacts API and how to resolve them.

## Working  with errors

This section captures a list of common HTTP errors you might encounter and possible solutions to fix them.

| HTTP Error Code | OTA Error Code | Description | Reason and Possible Fix |
|  --- | --- | --- | --- |
| HTTP 400 Bad Request | 150 | Changes are not permitted. | Can occur when trying to create a contact of type `general` using the `POST` request given they already exist. Try to update the existing contacts. |
| HTTP 400 Bad Request | 320 | Invalid value. | The API returns `errors.details` and `errors.description` that captures which part of the request body contains invalid values and a description to help you troubleshoot the error.  To know more about the exact fields with invalid values, parse the `errors.details.fields`. For some fields, the API also returns allowed values. |
| HTTP 400 Bad Request | 321 | Required field missing. | Use the `errors.details` and `errors.description` field to identify the missing required fields and a description to help you troubleshoot the error.  To know more about the exact fields with missing values, parse the `errors.details.fields`. |
| HTTP 400 Bad Request | 394 | Invalid item. | Can occur when you specify an unknown parameter in the request. Make sure to specify the right parameters. |
| HTTP 400 Bad Request | 450 | Unable to process | Can occur due to one of the following reasons:  - Incorrect endpoint URL/HTTP method or invalid JSON body. Make sure to use the correct endpoint URL/HTTP method or check if the request has a valid JSON body  - Specifying `Contract` as a `contact_profiles`.`type`. Because this contact type is not supported while using the Contacts API, use a different contact type. |
| HTTP 400 Bad Request | 497 | Authorization error. | The request contains invalid authentication credentials.  Provide the correct authentication details. |
| HTTP 404 Not Found | 635 | Not found | Make sure to use the correct property ID or check whether you have provided valid credentials to access the property details. |


## Quick Actions

→ To create and manage contact details, see [Managing contact details.](/connectivity/docs/contacts-api/implementing-contacts-api-ga)
→ To learn more about the Contacts API use cases, see [Contacts API implementation use cases.](/connectivity/docs/contacts-api/contacts-api-usecases/)