IP Restrictions — API access is restricted by IP & API Token.
If IP-based control isn’t whitelisted in Manage API IPs then API will not work properly.

Generate API Token

Generate an API token by navigating to Configurations → Manage API Credentials in the Admin area (left menu). In the API Credentials tab, click Generate New API Credential.

Manage API IP

Add remote IP  by navigating to Configurations → Manage API Credentials in the Admin area (left menu). In the Manage API IP tab, click Add IP Address button and enter IP address then click at save button.