We have seen how to add an additional repository on Ubuntu and it is a very simple process, but in some rare case we may get an error message that says:
Cannot add PPA: ‘ppa:<ppa_name>’. Please check that the PPA name or format is correct.
Most of the times the problem is caused by the CA certificates and to fix it we just need to give the following command:
sudo apt-get install –reinstall ca-certificates
After that we can proceed to install the repository as indicated.