Make sure you do not have another window opened up still . like your salvage window for base salvage bins. My example was I had 6 catalysts stored in my base salvage bin. I opened the window and took 6 catalysts out and then clicked on manage and tried to convert without closing the salvage windows. I had the same experience as you. I could select the combine window. Select the catalyst and select combine but it would never combine. I had to select cancel also. and saw that I only had 5 catalysts left. However, when I checked the salvage bin I found the catalyst was back in the bin. So, if that is what you did then you shouldn't have lost anything. just need to make sure to close the windows after taking the catalysts from the bins before trying to catalyze them.