Hello mates,
I'm having some troubles with WPML and i can't understand why because i have followed all instructions. (it's not the first time i'm using wpml)
The screenshot's are attached(they are in portuguese, if you don't have anyone who speak portuguese in support, i can translate to english the information.
Welcome to the WPML support forum. I will do my best to help you to resolve the issue.
We had the same bug in the past and it has fixed after installing PHP Multibyte String Extension on the server.
PHP Fatal error: Uncaught Error: Call to undefined function mb_ereg_replace_callback() in /wp-content/plugins/sitepress-multilingual-cms/classes/xliff/class-wpml-tm-validate-html.php:124
So please consult about this with your hosting service team. Refer to the following documentation for more details.