How to custom end date (validate) with Flatpickr

Hi, I am working on a survey that asks end-users to select a Start and End dates from a calendar (Flatpickr) using a Text Entry Form fields question. To validate the End field I've added a Custom Validation to the question (with an error message) to restrict end-users from entering a date that is earlier than the Start date entered (piped text). ! When testing, the survey does not accept any date even if I enter a date after the Start Date, the error appears and the user cannot move to the next question. Can you help? Thanks in advance.