Why does my gRNA not cut?

Dr. Jesse Boehm, Associate Director, Boehm Lab at the Broad Institute published an ancestral attribution to sgRNA cutting inefficiency in his published manuscript in Nature Communications in 07 June 2024 and in his abstract he writes:

“Our analysis suggests that for 1.2-2.5% of guides, germline variants in sgRNA targeting sequences reduce cutting by the CRISPR/Cas9 nuclease, disproportionately affecting cell models derived from individuals of recent African descent.”

He and his team developed AncestryGarden.Org

(At the time of writing the website was down.)