tick box options not showing

i use the tick box option on my form which displays and works fine but the notification mail does not show what has been ticked?

it does show the field name i assigned for the tick box section and underneath that it just has “-” and nothing else so it does not show the field name i assigned for each tick and does not show which was ticked by user

so on form i have

field section ” my tick boxes area options “

field choice 1
field choice 2
field choice 3

so user might choose ticking option 1 and 3

notification mail will show

“my tick boxes area options”

–

and thats all ( speech marks only added to highlight here )

any ideas why this is happening ?

https://wordpress.org/plugins/custom-contact-forms/