I haven’t got a clue how you have created this form with elementor, so I don’t know how it works.
This would also depend on what type of select field you are talking about. Is the field type “Select” or is it another field type that us using a select field to make choices.
More then likely there is one of two things happening. 1) When saving the value the corresponding field key reference entry is not being created in the DB 2) The value is not stored in the correct format for ACF to understand the data.
More information will need to be given about the field type and how the data is being updated in the DB.
