Error 500

I just installed and activated WooCommerce and woocommerce-mercadopago and saw the same error:

 PHP Fatal error:  Cannot declare class Rest_Client_Abstract, because the name is already in use in wp-content/plugins/woocommerce-mercadopago/includes/module/sdk/lib/rest-client/class-rest-client-abstract.php on line 21

I edited that file and wrapped the whole Rest_Client_Abstract class into that code:

 if (! class_exists('Rest_Client_Abstract') ) {
...
...
...
}

Then I received another similar error:
PHP Fatal error: Cannot declare class MP_Rest_Client, because the name is already in use in wp-content/plugins/woocommerce-mercadopago/includes/module/sdk/lib/rest-client/class-mp-rest-client.php on line 19

I edited that file too and wrapped the MP_Rest_Client class into that code:

if (! class_exists( 'MP_Rest_Client' ) ) {
...
...
...
}

Then, it worked.
If you make those changes, test your plugin to make sure there’s no issues with it.
I have no idea why it tries to load those classes twice.

The profiler can’t work with just a button in the admin bar, because there are some AJAX requests to be processed in the background and so far they are only available from the main profiler page.

The input fields on the profiler page are not saved. Maybe I will add a possibility to temporarily save them inside a cookie for the current session.