Full cartridge, no insulin coming out during load

I just changed my pump. I filled my cartridge with 250 units of insulin and let the tube fill. After 15 units or so I noticed that no insulin had come out of the tube. The pump said something along the lines of “no insulin detected”. I took it out and tried reloading it with the same results. I got nervous, like where is the insulin?! So I put the syringe back into the cartridge and sucked out the insulin… not sure what happened there. Just wanted to see if this has ever happened to anyone else?