Hi @arshaim39 
It looks like you might want to use this method to set the checkbox value:
https://api.onlyoffice.com/docs/office-api/usage-api/text-document-api/ApiCheckBoxForm/Methods/SetChecked/
We’ve come across a similar challenge with checkboxes before in this thread:
https://forum.onlyoffice.com/t/the-radio-box-created-using-builderapi-could-not-be-selected/5187
Could you let me know if I’ve got your request right?