If your Tahini is not blending properly in the blender, there are a few potential causes to address. First, ensure that you have enough quantity to effectively engage the blender blades. Secondly, make sure that the sesame seeds are adequately toasted and cooled, as dry seeds may impede proper blending. Lastly, check if there is enough liquid in the mixture, as Tahini requires some oil to facilitate smooth blending. Also, I would suggest using a high-power blender for optimal results.