Check:

1. That the process has read permissions to the configuration file
2. That there are no errors in the configuration file
3. That you are not specifying to use an alternate file when you run Odoo
4. That the environment variable ODOO_RC is not defined
5. That an alternate file is not being found in  $HOME/.odoorc

See https://www.odoo.com/documentation/15.0/developer/cli.html#cmdoption-odoo-bin-c