Poor quality or too much dna will result in no amplification. Does your ladder show on the gel? Does the positive control sample work?.Is there a strong blurry smear of primer dimer at 50bp or smaller?

You can measure the concentration of your DNA stock solution using a NanoDrop or similar device. Based on this, you can then make up PCR working stocks of 50 ng/uL - this also reduces the chance of contaminating your stock solution.

No amplification can be caused by a lot of common problems. You can narrow this down a lot by running control reactions: positive and negative controls for your genotype of interest, AND a known-good control primer set that should amplify if any mouse DNA is present. When I was doing genotyping I used to mix the genotyping primers and control primers (GAPDH gDNA) in a single reaction. This way two bands is positive for the transgene, one band is negative, and no bands is a reaction failure.

If control primers are working, the issue is with your genotyping primers. Either the primer set is bad (dimer problem, running at the wrong temp, a primer is around the wrong way, or something like that) OR somehow all your samples are transgene negative.

If control primers are not working, the problem is with your samples or PCR. Check the sample concentration and purity - is there any way it contains PCR inhibitors? It might need to be concentrated, diluted, or cleaned up. Check your reaction setup to make sure all reagents are included at the right concentration, and double check your thermal cycler settings. Finally, make sure that if you're using a hot start polymerase, you include the hot incubation to initialise the PCR.

Good luck! :)