Not quite two years ago, after Microsoft bought Skype, they put the kybosh on Trillian (and other 3rd party) multi instant messaging programs access to Skype.
I’m not saying that Trillian dropped the ball, but they did, as Miranda and other multi messaging programs have fixed this issue, but Trillian didn’t.
Luckily, someone figured a work around for this. Install OLDER version of Trillian, get accounts set up. Shut it down. Locate SkypeKit41_noid.exe and download it. Copy it into Trillian directory. Rename it Skypekit.exe (just delete the original one, as it no longer will work anyhow).
Install newest version of Trillian, and once again, Skype is functional. Not sure how long this will last but I have been.. well was using it, on my desktop for over a year, and currently using it on my laptop.