we need details like the product size, the annealing temperature, the concentration of dna added, the cycling parameters and ideally a picture of the failed amplification. I would measure the od of the dna and use about 50ng DNA and run an annealing temperature gradient or if that is not possible then run the pcr cycle with a low annealing temperature to get a dirty result then raise the annealing temperature until the amplification become a clean single band

TLR 2 genomic region. 1280 bp. Gradient PCR annealing, 50 degree +_ 5 degree. Extension- 1 min 50 sec.....DNA 4 UL. Diluted.(1:5), No spectrophotometer. DNA isolated from blood qiagen kit.

1 µL genomic DNA

0.50 µL 20X primer (includes F and R in the mix)

5.0 µL of Qiagen Multiplex PCR Master Mix

0 µL or 1 µL Q-solution

Adjust water to bring up to 10uL volume

You can run samples on a gradient with standard conditions to determine the anneal temp if you are trying to figure that out (I do 50-65 to start).

Your large-ish fragment size might be an issue.