[Resolved] Fatal error after updating WPML to 4.0

Okay as promissed here is the errata page for this issue that we have found: https://wpml.org/errata/fatal-error-upgrading-wpml-method-wpml_admin_menu_item__tostring-must-return-a-string-value/
In that page, there is also a workaround/fix that you could give a try.

@veerle Delporte I suggest that you enable debugging in WordPress and open a new ticket as this could be a compatibility issue.
To enable debugging you need to set these options in wp-config.php
above the line that says:

// Turn debugging on 
define('WP_DEBUG', true); 
// Tell WordPress to log everything to /wp-content/debug.log 
define('WP_DEBUG_LOG', true); 
// Turn off the display of error messages on your site 
define('WP_DEBUG_DISPLAY', false); 
// For good measure, you can also add the follow code, which will hide errors from being displayed on-screen 
@ini_set('display_errors', 0); 

@kurtp If you cannot access the dashboard, you can either use your hosting panel file manager or FTP and go to /wp-content/plugins/ and either rename or delete the wpml-media-translation plugin. This will not make you lose any information and once it is done - you can re-install the latest version that has a fix for this.

@valeriek-3 You might be having a separate compatibility issue.
I suggest that you do these steps:
-Check if you are using all latest versions
-Test in a minimal setup - only WooCommerce and WPML plugins perhaps?
-Check with a default theme like TwentySeventeen
If that does not help - I suggest enabling the debug in WordPress and checking for errors and opening a new ticket in our forum.

Please follow my suggestions @valeriek-3
If it is not working and it is not related to this topic here, please open a new ticket and our support specialist will handle at first opportunity.