1)the soil sounds like it is NOT well drained.... keeping the mix damp not wet ALSO mist the foilage
2)remove a cutting & check to see if its soft starting to rot

Lavender tip cuttings are reliable rooters, but usually take about 30 days. They must be either carefully tented or misted for the entire time. The soil should be very well drained, as george mentioned. I use a mix of 80% perlite to 20% peat. If bottom heat is available it will help. Al

Thanks for the posts. I made a mixture of perlite and peat moss as suggested but still no success. I guess I have to experiment more. How about the temperature? I have them in the shade but the weather is very hot (90-ish F) and humid.

I do my lavender cuttings in the winter, with the air temperature averaging about 50 degrees, the heat pad for bottom heat set at 70 degrees. Expect about 30 days to root growth to start. Mine are tented, and vented every other day to prevent mold growth. Al