Hi,

Please make sure you have followed the proper structure when creating a field. 
If you are creating the field in new custom model, Follow the documentation given below:
https://www.odoo.com/documentation/16.0/developer/tutorials/getting_started/03_newapp.html

If you are creating a field inside an existing model, then follow the blog given below:
https://www.cybrosys.com/blog/how-to-add-custom-fields-to-existing-views-in-odoo-16

Hope it helps

Hi, 

Please follow following link to resolve the error:

https://youtu.be/Xya_fCNr6tw

Thanks