If you are extending a view, check if your model name is the one of the parent view. To spot invalid syntax, go to an online relax ng validator like https://www.liquid-technologies.com/online-relaxng-validator. Add the contents of your view in the first input field and the contents of odoo/odoo/import_xml.rng in the second and validate. The errors here will give you precise info on the error. Here is an example ...