Order Form: Cannot find form calculation field under Get Price From

I have used form calculation widget to calculate the sum of ticket sales. I have followed the instructions above to pass the calculated total to the payment field; however after selecting 'user defined amount' in the payment type i do not get the the pop up message as in '3' above and the only options available to me in then'Get price from' field are 'None (manual)' or 'clickto37'. Can you advise why I cannot see the 'calculation widget' option? Thank you

The 'clickTo37' is the internal field name of the form calculation widget field on your form, so it is fine to select it as the 'Get Price From' field.

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