A couple of other people reported the same error. When I googled "wordpress Class 'Translations' not found" then I found one person saying that it's possible not all the files in "the wp-includes/po directory" were uploaded and one suggestion saying that you need to "Open up the dashboard (/wp-admin) which will prompt to update your database…". Apparently, they're suggesting that once you update your database, it will work. Since I don't know anything about the wordpress software, I don't know if that's the case. However, the error message is suggesting that something is missing - either a file that the software is calling or a field in the database. I'm sorry that I'm not more help.