You will need to provide a little more information. It could be due to permeabilization issues, using a conjugated Ab that is not recommended for IFC, lack of substrate to bind an antibody, inability of the conjugated secondary antibody to bind to your primary antibody, and even poor transfection efficiency if your looking at an overexpressed protein. Cy7 in itself will not stain cells, it is just a fluor. Ill be happy to help you try to figure it out if you want to provide more information.
Other channels often provide "high" fluorescent and are thus easily visible through the ocular. On the opposite, Cy5 and Cy7 may often only be visible when using longer exposure times during imaging with a fluorescent camera. In summary, the signal may be too weak.
Overall you will need to provide more information. Often the supplier of your antibodies has a trouble shoot pdf that may help
Thanks Jason and Konstanin for your time and response. I usually used Cy5.5 but this is first time that I was trying to excite Cy7. I have always see good fluorescence signal for Cy5.5, FITC, TAMRA labeled cells. I am not using any primary or secondary antibody. I have this NHS ester version of Cy5.5 and Cy7. I have contacted GE for technical support, if I will here something I will share here.