Error: invalid_client

You need to add this to your functions.php file instead:

add_filter('login_with_vipps_test_mode', function ($true) {
  return true;
});

Same with “login_with_vipps_test_clientid” and “login_with_vipps_test_clientsecret” if you want to have separate keys for test mode.

– this will turn test mode on. Remember to remove this before going live.

Is there a reason you prefer to test login in the dev environment instead of the live one? There is no commercial activity with login, and all who are going to test is going to have to install the test app using testflight etc.

Hi, it’s works. So better is to switch to the live one. Ok we will do it. I didn’t know that. I’m just implementing this plugin.
Thaks it’s works any way.

One more question. You have mentioned that the login option is not commercial. But what about requiring payment is it not connected with login ?
https://github.com/vippsas/vipps-login-api/blob/master/vipps-login-recurring-howitworks.md

They are all separate plugins. The login plugin can be used also with no ecommerce installed.

My note about the login-plugin is just that as it is free to use the live version, there is usually no need to use the dev environment for testing (no money changes hands in any case). You may have other reasons to use the dev environment of course.