Having the same problem … on mac.
$ git push ionic master
firstname.lastname@example.org: Permission denied (publickey).
fatal: Could not read from remote repository.
Please make sure you have the correct access rights
and the repository exists.
This is how I solve my problems due to SHH_KEY problem.
- recreate my ssh key
$ ssh-keygen -t rsa -C “email@example.com
- Copy my ssh key and add to my ionic account SSH Key Setting. (Under user profile)
$ cat ~/.ssh/id_rsa.pub | pbcopy
- View my current SSH key folder
$ cd ~/.ssh
- Look for ionic folder. If exist please follow next step else go to step 5
$ cd ionic
- You will see a file with  & .pub inside the folder. delete all the files by using rm. replace  with the number found in your ionic folder
$ rm 
$ rm .pub
Relogin your ionic account using ionic CLi
$ ionic login
After that just login using your ionic credentials. You should be prompted as follows:
Looks like you haven't configured your SSH settings yet.
? How would you like to connect to Ionic Pro?
I just choose : Automatically setup new a SSH key pair for Ionic Pro
enter passphrase if required.