Hi, You can't add computed/related field to search or group by if the store Parameter is not set to True or if the computed field not have search parameter. 

Note: By default store parameter is set to False. 

SO you have add store = True to the related fields.

For computed field you can set store=True (but this will change the calculation of the field to be recomputed once the one of depends fields changed), If you don't want to change the store for computed field you can add search parameter which called method you will write to search in computed field.

Please read more details in Odoo ORM