Question: TV reception

Just installed an RCA ant751 antenna with RCA pramp1. Both were installed using instructions.
One problem: I am receiving no VHF channels, both high band VHF transmitters are in the same vicinity as the UHF towers I am receiving. The towers are about 45 miles away; I am receiving 31 UHF channels but no VHF. TVfool located the towers for me, and I used a compass to aim the antenna within (+or-) 5 degrees of proper location. I am wondering if the pre-amp is filtering VHF signals? or if some other problem exists, or new antenna indicated?

Thanks for anybody's input, I am new to this.
The separate combine switch set wrong on the pre amp. I'm not familiar with the product, but have read of common set up mistakes made with it. It sounds like the switch is set to separate, and the antenna is hooked to the UHF side. I'd have to look up the instructions to be of more help.
@ RF Steve
This Antenna/PreAmp combo is supposed to be one of the best rated on the market. The switches on the box were as you suspected, I changed the settings..."Voila".. 41 channels now, including the high-band VHF,