Q.Why don’t my gardenia cutting have visible roots?
The cuttings were taken in late December. I have cut off the lower leaves, put in a mix of sand, soil and peat in a 1 qt. pot in early January, kept them warm and moist (not wet). The cuttings were kept in a south facing window until it was warm enough to put them outside. We live south of Houston so they have plenty of humidity. I went to repot them this weekend (end of June) and they still have no visible roots! I thought surely they would have visible roots by now and was repotting them to keep them from being root bound and hard to separate. They are outside on a ledge where they get bright indirect sun. 2 of them do have a new growth bud on the top, one does not. I re-dipped in rooting hormone and placed them back on the same outside ledge.

Sometimes this just happens. The best thing to do is what you have already done. Re-dip and hope for the best. You may have some success with letting the soil dry out slightly. Not bone dry, but enough to see that it needs a little water.
https://www.gardeningknowhow.com/ornamental/flowers/gardenia/propagating-gardenias.htm