Is there an explanation to why my eyebrows haven't held the pigment? I am 55.

It has been 4 weeks since I had my Microblading done, there is no colour or strokes left.. I did all of the aftercare properly, my technician has been doing Microblading for years and all of her other clients have turned out perfect. The tattoo has disappeared, is there an explanation to why my eyebrows havnt held the pigment. I am 55.