Logging into your GLPI installation from Gapp (A GLPI app) is not possible due to this error message:
SSL Certificate error - Seems like there is an error with GLPI Server SSL certificate you are trying to access
As for Android Java reference CertPathValidatorException:
An exception indicating one of a variety of problems encountered when validating a certification path.
The most usual problem is a self-signed certificate or a badly configured SSL web server.
Additional info: https://developer.android.com/training/articles/security-ssl
- If your GLPI installation is not published on the Internet, you won’t be able to get a proper SSL certificate. Drop https and use for http.
- If it is exposed to the internet, you need to properly configure your webserver. Go to https://www.ssllabs.com/ssltest/ and configure it to get an A.