Some of the fields such as the "Status" field can have workflow transitions defined as part of their tracker configuration. You must consider such transition rules when you create your mapping. If you map a field violating a status transition workflow, the mapping can fail.
Here's an illustration.
Suppose, you have a Jira workflow configured for the Status field, which is set to "Open" initially (the default value), transitions to "In Progress" before you can set it to "Pending".
In this case, when you create a field value mapping for the Status field, you must make sure that you do not select "Pending" as the default value in Jira as illustrated in the following image.
In the case of Jira, you can click the workflow icon next to the Status field to view the Jira workflow definitions in Agility Connect.