1) Maybe there is genomic DNA in the bands (target DNA) (because genomic DNA has a large molecular weight, it cannot come out of the sample well)

2) Maybe there is protein in the bands (target DNA) (because protein is with DNA, the molecular weight is very large, so it cannot come out of the sample well)

All in all, the extracted target DNA is impure, and there is genomic DNA or not separated from protein, so the molecular weight is greatly increased. Genomic DNA or not separated from the protein, thus leading to a much larger molecular weight, can not run out of the upper sample well

There is another possibility, that is, your voltage is not added, or your electrophoresis buffer is prepared with distilled water, there is no ions, can not be conductive, and the DNA did not swim.