In dashboard charts, we don't see Elements Connect fields value but their key or an empty value
A non supported Velocity variable is used in the query:
$issue- when an Elements Connect field is displayed in a statistical gadget, the $issue context is not available
$userInput- this variable is only available when editing field using the Autocomplete editor
Write a custom query for the dashboard view (from the Display view configuration).
Remove dependencies to $issue and $userInput, use $currentCustomfieldValue instead.