OK, seems to be because you have the "Filter Data" in the filter settings for that element set to "Recorded data" (well, "Global", which is taking your global default). And none of the rows in the table have a value set for "type de finance d'entre".
The difference between the two "Filter Data" modes, for join elements is, is:
"Recorded Data" only shows you options that actually exist in the form's data.
"Show All" shows you all possible options, ie. all options from the joined table.
So say you have a "Contact" form, with a join to "US States". If you have your "Filter Data" set to "Show All", the filter dropdown will show you all 50 states, regardless of whether any of those states have been selected in submitted Contact forms. If you have it set to "Recorded Data", and only 3 states have been selected in all your submitted Contact forms, the filter dropdown will only show you those 3 states.
So because that join element has no data in any rows, the dropdown for the filter will be empty when set to "Recorded Data".
I changed it to "Show All", so you now see all three possible options from the joined table. Even though none of those will yield any results.
-- hugh