Here are two common reasons this may be happening:
If you are not able to view the fields that you have created while customizing, please check if you have marked those fields as protected. You can check this in the fields setup > Data Capture tab of the field that is not visible while customizing the template. In the Data Capture Tab you will find a check box for “Protected Fields”, if this box is checked, uncheck the box, save it and commit it and you will be able to see the field while customizing the template.
The stacking order of the fields should be between 1 to 100. Stacking orders between 101 to 110 are meant for overlay fields and do not allow the user to edit the fields. You can check this option in the Format Tab of the Field in e-Doc Builder. Path: e-Doc Admin > Template > Edit Template > Field Setup > Affected Field > Format Tab > Stacking Order.