SSL Error 61 with Citrix Linux Receiver

First ensure you're using the latest client

Now add more SSL certificates to fix SSL Error 61

sudo ln -s /usr/share/ca-certificates/mozilla/* /opt/Citrix/ICAClient/keystore/cacerts/
sudo c_rehash /opt/Citrix/ICAClient/keystore/cacerts/

For a more full guide on running the Citrix Linux Receiver, the Ubuntu help seems to have most points covered:

If this helped, let me know :)