calendar not working due to javascript error

This is a problem that you fixed and is now back after updating, even though I use a child theme. The calendar in formidable forms is not popping up. I contacted them and this is what they said:

There is a JavaScript error on the page that is preventing the
calendar from working:

Error: TypeError: $j(…).simplePlaceholder is not a function
Source File:
http://www.grocerykartbythebay.net/wp-content/themes/HighendWP/scripts/jquery.custom.js
Line: 224
This error is coming from your theme, so I would recommend letting
them know about the issue.

How do I fix this again? Or do you need my login info? I will provide it in the next message.