Problem after updating to piwik 2.7 (no replies)

Good afternoon.

Today after updating to 2.7 it said that the update was done, however when I entered the page I received this message

Fatal error: Class 'ComposerAutoloaderInitc18f4863fe5a9b19f3f6cb78af7aad2a' not found in pagename/vendor/autoload.php on line 7

Can someone help me with this? How can I fix this issue?

Thank you