If you use the Pro Version, you can find the latest version from webnus.net dashboard > download tab
5- If you use the cPanel so, please upload it to the above directory and extract it there. If you use FTP access because you cannot extract zip file there, you can go to WordPress dashboard > Plugins and upload again MEC-lite.
By now your issue should have been fixed, just need to log in to your WordPress dashboard and use it same as before.
After deleting MEC-lite your WordPress access would be back, so you can get a backup with extra plugins then.
To put it simply, a PHP file changed the encoding and that’s why the error occured. If you upload MEC again the encoding will be back to its previous state.