Problem: The client is attempting to set up the OTGS installer for WPML in two languages on a subsite of a multisite network but encounters a Curl 28 error during the registration process. Solution: 1. Ensure that only the main site domain is registered on wpml.org. Subsites will use the same site key once the main site is registered. For detailed steps, refer to our guide on Multisite Support. 2. The Curl 28 error typically indicates a temporary connectivity issue. To resolve this, generate and register a new site key for your main site. 3. Contact your hosting provider to request whitelisting the following domains:
wpml.org
cdn.wpml.org
api.wpml.org
api.toolset.com
cloudfront.net
For more information, visit WPML plugin cannot connect to wpml.org. If the problem persists, please open a new support ticket. We highly recommend checking related known issues (https://wpml.org/known-issues/), verifying the version of the permanent fix, and confirming that you have installed the latest versions of themes and plugins.
For further assistance, please visit our support forum.
