If you are trying to update the plugin and you get the error message: “could not copy file”.
This can happen because of two reasons:
1. Your Linux server does not have correct permission / ownership over the files. Make sure that you set the plugins files to 664 and that the user that manages the server can also manage the files.
2. If you are on Windows running a localhost such as XAMP or WAMP, this problem can happen if the file path is to long. For example. C:\files\host\blah\more\www\wordpress_dev1\
There is a ticket in WordPress core to fix this issue (https://core.trac.wordpress.org/ticket/38231) but for the time being, you will either need to manually update the plugin or shorten your file path.