Back-office access after StartTag error

If your store is running a PrestaShop version lower than 8, your back-office access may be blocked following this error message: 

If this applies to you, here is what to do: 

• Connect to your server via FTP
• Go to the /config/xml/ folder
• Delete the following files: 

must_have_modules_list.xml

modules_native_addons.xml

default_country_modules_list.xml

• Try to connect to your store again. 

If you still cannot access your back-office, please contact support.