T3 Plugin is a definition of cancer and I am not sure how other make it work but after 3 years of using it it's just absolute rubbish! seriuosly after numerous updates it was getting worse and worse until now stoped compiling the Less to css completely
at the begining the css compression was broken then fixed then broken again. The less compiling was absolute nightmare all the time. I needed to switch to developer on/off save code/ complile few times etc to make it work.
I am not sure if you aware so i just wanted to let you know.
I am using default t3_bs3_blank
If you aren't developer and planing on using this just setup your own less compiling on save and use custom themes as this will save you hundreds of hours... like seriuosly takes like 1min to compile code?