Your list views broke because <tree> became <list> in Odoo 18

Odoo 18 renamed the <tree> view tag to <list>. Every list view in your module needs updating, or it won't load. Simple, mechanical, and easy to miss one.

Three places it hides

The view definition itself:

<!-- before -->          <!-- Odoo 18 -->
<tree string="Orders">   <list string="Orders">
  ...                      ...
</tree>                  </list>

The view_mode in window actions:

<field name="view_mode">list,form</field>  <!-- was tree,form -->

And xpath expressions in inherited views — expr="//tree/field[...]" becomes expr="//list/field[...]". Miss any one of the three and you get a validation error or an action that won't open.

Send us the module. We rename them all, install on Odoo 18, and test. Try it live, then $50 to download.