Error message while trying to set up MF Connect between Octane and Jira

We are trying to set up MF Connect 4.4.1 in a development environment with Octane 15.0.20 and Jira 8.13.3.

The first synchronisation we would like to set up is for defects only.

We have created a datasource for Octane and a datasource for Jira with a dedicated sample project and board, as asked.

When we try to create the connection, we get an error message on the second step (Types and fields) while trying to add the types mapping :

SyncableFields

Jira Anomalies: type: Anomalie, does not have syncable fields. Values cannot be manually edited.

"Jira" is the name of the Jira datasource, Anomalie is the french word for defect and the name of the corresponding type in Jira.

We can't figure out what is going on, expecially what makes a field syncable or not. Many fields are visible on Jira Item Create Screen.

Has anybody faced the same problem and knows how to solve it ?