my suggestion was to open all intensity bands after you applied split and orbit files. If all show an image, you can proceed.
You can check if all bands of your back-geocoded stack contain information by making RGBs as described here: Fault marking by InSAR Data and difference between SLC_1SSV and SLC_1SDV?
If the images are not properly aligned, the interferogram will fail. Based on your information, it rather looks like some dates remain empty after back geocoding.