I'm not familiar with that particular yeast. I've never worked with it. I don't know if it is typically a slow starter.
Are you sure your temperature is warm enough? In colder environments it may take longer to noticeably start. Did you check for optimal temps for that particular yeast? I'm sorry if I'm being too obvious, but since I don't know you or your technique I thought it best to rule that out.
I did run into a similar problem, quite recently, when I chose to settle for yeast that wasn't as vigorous as I'd like. It's a long boring story, but I had the choice to drive a long distance, wait for mail order, settle for what the usually reliable place nearby had on hand, or put off mazing all together. I ended up with a 4 month old (within recommended limits) smackpack of Wyeast dry (flavor producing) liquid yeast, not my first or second choice for this batch, but what they had. Then, It didn't puff up well, it was semi puffed at the end of the recommended wait time. I knew the risks and decided to pitch it anyway. (If you aren't familiar with the product there is nutrient and liquid yeast inside a plasticy envelope, you smack it to break the membrane separating them within the envelope, and shake to mix them, then wait. It's a sort of a ready made starter, I prefer to do my own).
After 36 hours I moved the batch to a glass carboy so I could see better, and maybe get a little more oxygen in there in the process. PH was good, temp was good, nutrients were good. After 48 hours, there wasn't noticeable bubbling, but I could see clouds of yeast floating in layers, like horizontal stripes. Shortly thereafter it started going like wildfire. I don't know if it was the additional oxygen, or simply time for the colony to grow. Based on the clouds of floating yeast I suspect and the lack of vigor in what I pitched, I suspect it was the later.
I hope your problem is solved before you get a chance to read this.