Problem: After setting up a staging environment for the site and performing a search-replace operation, a warning appeared in the admin panel indicating a migration service error with the message 'Migration code expired, please generate a new one'. Solution: We recommend generating a new migration code. You can do this by navigating to WPML>>Translation Management>>Tools>>Connected sites>>Enter the connection key of another site. After updating the migration code, please try connecting the staging site with the live site again and let us know if the issue persists.
If this solution does not resolve your issue or seems irrelevant due to being outdated or not applicable to your case, we highly recommend checking related known issues at https://wpml.org/known-issues/, verifying the version of the permanent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. Should you need further assistance, please do not hesitate to open a new support ticket at WPML support forum.
