New tire Flat after 15 miles?

Originally Posted by ZeroZeta

So I finally mounted my new Pole Position S04s on the car. Drove a little bit and found my left rear was flat.

I removed the wheel and can't find any visible damage to the tire. I will be doing the soapy water test around the valve stem tonight.

My question is how common would a valve/tpms leak be and can anyone think of any other reason a brand new tire would go flat or anything I might be overlooking?

I had the mounting done at Discount (after fighting with them a month to get the tires so I wouldn't be surprised if it was related to their labor.)

Thanks in advance.