I would suggest starting at the basics and insuring that the client is correctly installed on the system and that the Excel add-in is both installed and the system has the client registered to be able to correctly use that add-in and all third party add-ins that would be needed to used (such as excel, word, and other third party add-ins).
In order to install and register the client for use with the third party add-ins you will need to have admin privileges, turn off any anti-virus, and place the User Access Control (UAC) to the lowest setting of "Do not notify" or have it disabled entirely by your IT department for the duration of the client install. Right click on the IE browser icon and select the "run as Administrator" option for the initial installation and then visit your browser to install the client fully. Once it is installed then go back to the landing page http://<ALM URL>/qcbin/ and once on this landing page select the "tools" option and on the next page select the "Client Registration" section and once there scroll to the bottom and select the "Register Client" link and run it.
You will need to then obtain and install the Excel Add-in from the Microfocus Marketplace for your current version (only one Excel add-in is allowed so if you have another ALM version's add-in installed then uninstall it first). Once this is doone you should be able to connect as you have in the past.
If you encounter any issues I would suggest getting your IT department and ALM admin (as well as possibly your support team) involved to correct any issues.
Hope this helps,