I think this will answer your question:
val stringDate = expiration_button.text.toString()
val formatter = DateTimeFormatter.ofPattern("dd/MM/yyyy hh:mm");
val dt = LocalDate.parse(stringDate, formatter);
Edit 1:
It’s probably crashing because you are using a 12hr Hour, instead of a 24hr pattern.
Changing the hour to 24hr pattern by using a capital H should fix it:
val dateTime = LocalDateTime.parse(stringDate, DateTimeFormatter.ofPattern("dd/MM/yyyy HH:mm"));