Installing and using citrix under linux might be a bit more tricky than it may appear on first glance. Here are a few steps to make it work.
1. Remove old installation, if needed.
sudo apt-get remove icaclient
2. Download Receiver for Linux. Look for it here: http://www.citrix.com/go/receiver.html
Make sure you have the correct version. This is probably under “For 64-bit Systems”
3. Open the download, and install through package manager.
4. Link certificates:
sudo ln -s /usr/share/ca-certificates/mozilla/* /opt/Citrix/ICAClient/keystore/cacerts
5. in firefox, set Citrix Receiver for Linux plugin to Always Activate.