Unable to write file
Make sure that the folder /var/www/vhosts/examplesite.com/httpdocs/wp-content/plugins/files/civicrm/ is writable to the webserver user.

The simplest solution is to set the permissions on that folder to be read/write for ALL users.

A better solution is to configure the permissions so that they are open to your user account and the webserver alone, but not other users on the same hosting server. How you approach this depends on the hosting environment and probably requires learning how to manage filesystem permissions.

See also: 


Are there recommended directory ownership and permission settings for CiviCRM files?
CiviCRM does not have permission to write temp files on new server