And I added this IP to the Hosts file with the host name of my portal
Typically HTTPS certificates are issued for a hostname, not an IP address.
Did you edit the hosts file on your android device or your GIS server? I'm thinking likely GIS Server. If that's the case, how will the mobile device know how to reach the GIS Server?
If you edited the hosts file, why are you trying to connect via IP?
Hosts file is for name resolution, and you're trying to connect via IP.
You'll need to provide more details. As it is, there's too many variables to work out and your workflow doesn't make sense.