There may be many reasons for this. The variant may not lie in exonic regions, none of the capture kits cover this particular variant, there were no carriers of alternative alleles, or this particular variant was removed due to bad quality before variant calling. Because of this, we are unfortunately not able to pinpoint the exact reason for a missing variant. However, variants that had quality issues after variant calling are left in the data, but they have only the pre-qc allele frequency.
Of course it is also possible that variants are not found because the syntax has been wrong. Therefore, we suggest you to check the search instructions, just in case. Please also note that the positions are in GRCh37, not GRCh38.