I am trying to generate stable knock-in variant RPE-1 cells to model human variants using CRISPR with provision of repair SSODN's. I have previously used my guide RNA successfully to generate gene knockouts - getting around a 7% efficiency. This time, I transfected in my guide RNA complexed to an ATTO-tracr-RNA with PX458 Cas9 plasmid and my SSODN repair template. I then did index FACS sorting and have grown up clonal populations. I have sequenced over 100 clones so far, all of which are wild type. Does the presence of the SSODN inhibit the ability of PX458 to create knock-outs through the NHEJ pathway? Or does the lack of any knock-out identification so far suggest that something has gone fundamentally wrong? Many thanks for the help.