When migrating from Jira Server to Jira Cloud, please follow the recommendations below:
Do not delete the existing Jira integration in Zephyr. Just edit the settings to point to the new Jira Cloud instance. Otherwise, all the mappings and links will be lost.
In the new Jira Cloud instance, the project name and key should be the same as those you have in Jira Server.
After connecting to the new Jira instance, click Update Webhook to recreate the required webhooks: