Atom shows there is a new version available but the version fails to install. You might have an error message showing a permissions error for example:
or it will say downloading but forever loops without restarting or updating.
You need to fix one or more of the following directories:
Do the following:
And then execute these steps for each directory listed above in order:
stat -f "%Su" [directory]
sudo chown -R $(whoami) [directory]
Once you've done the above for both directories, start Atom normally and attempt to update