You are getting argument list error as there are large number of files.
Or you are getting an 500 error. If you are getting a 500 error then your files need to change to 644.
With this solution you will be up and running in just a few minutes.
You can use the following command to change only the file permission to 666 inside a directory or to 644.
This command will not change permission of the folders present inside this directory
find . -type f | xargs chmod 666
You can modify back to 644 or from 666 as below.
find . -type f | xargs chmod 644