saocom level c product problem

I have the SAOCOM level c products which were already processed with radiometric calibration. now I am trying to do the terrain correction for those products in order to get those products georeferenced in the SNAP software using the tool range doppler terrain correction. but, it shows like there is an srgr coefficient error.
Then as I go through the snap forum, I found that I can do the same thing with the option of SAR mosaic in the snap toolbox. but it shows that the tool is not responding.
please give me a solution to get my products geo-referenced.