The following article describes some known issues that you might encounter when installing and using the CKEditor for Joomla! extension.
Error Message Displayed When Uploading the Extension to the Server
When trying to upload the CKEditor for Joomla! extension to the server with the Joomla! Extension Manager you may see the following error message:
"There was an error uploading this file to the server"
A possible reason for this is that your server blocks the upload due to the size of the file. Go to the php.ini file and find the upload_max_filesize instruction. Its default value is 2M, but this setting will not allow to upload files larger than 2 megabytes to your server. It is thus recommended to increase this value to a bigger one, for example 8M to accept files with a maximum size of 8 megabytes.
Save the php.ini file and restart the server.
The CKEditor for Joomla! extension should now be successfully uploaded.