The humidity of your room might be too low for the adhesive. You can increase it by using a humidifier. You can also increase the drying speed of your adhesive by using our Glue Accelerator (see product page for details). We always recommend to have few different adhesives for different humidity/temperature. Adhesive might not dry fast enough, on customers natural lashes, if : lashes are too dry, if they are on hormonal treatment, if you didn’t wash eyelash cleansing foam well. Please double check with your client.