Save checkbox in form - Dynamics CRM 365

Hello dears. I have created a checkbox with the following manual. However, every time I save and re-enter the form, the checkboxes appear unchecked.
Is there any way to save the checkboxes that the user has marked?

I use the version of CRM 8.2.2.112

Thank you

https://mahadeomatre.blogspot.com/2015/02/convert-option-set-to-multi-select.html?m=1