I'm having a very hard time trying to screen for my inserts-of-interest. I'm running a 1% agarose gel looking for constructs of base pair length between 1,500 to 2,200 bp. I've narrowed down the main difference between the already-used vectors and these vectors. The pET28 vectors worked fine with the T7 primer mix, but the vectors I'm having trouble with are all pET15 vectors which I've used T7 primers on as well. I've ran the exact protocol as stated for NEB's Phusion Polymerase reaction. Why am I not getting bands or what could have possibly gone wrong? I appreciate the help.