BCA concentration measured protein concentration 3mg/ml, but after adding buffer found no protein bands appeared, what is the reason?

BCA concentration measured protein concentration 3mg/ml, but after adding buffer found no protein bands appeared, what is the reason?

It is recommended to conduct a comparison experiment, set BSA as a positive control, and add buffer at the same time as the protein sample lysate to mix and boil the denaturation, on the sample for electrophoresis to observe the bands.