Coming back to where you said "In my flow I see that the debug after the dropdown selection is not executed" I suspect it IS happening but something else happens.
I suppose this is because in the moment I select the option (for example 81), I have the Connection lost.
I extract the part of the flow where the problem arises. I also disabled the node linked to the dropdown node, but it is the same. So I don't know what I can share that can help to solve this issue.
And the other important element is that if I run the flow in local (I mean the flow is located in my PC and query to the same database are perfomed), it works (no error of connection to the SQL database appears)!
Really, I don't know where look to find the problem.