SSL Tracking - is an option to provide information security. It encrypts the data transferring between client and server through HTTPs.  Please make sure the SSL certification has been installed on your domain.
If SSL certification has been installed on your Tracking Domain, you should go to "Setup > Setting >  Tracking Setting >  Tracking Domain > Manage Tracking Domains > Edit > SSL Status > Installed" to turn on the SSL certification. The "SSL Tracking" button can be turned on Manage Offer > Offer Detail >"General" page
* All tracking links generated before SSL tracking installation can not be changed. Once SSL certification installed and turned ON, offer's tracking link will be look  like: https://networkid.fusetracking.com/tl?a=X&o=X.