It’s disappointing that your rehab hasn’t worked out. I’m also deaf in one ear only. Had the cochlear implant done about 8 months after the sudden deafness (SSHL). The two ears sound completely different!
For my rehab, it was zero technology at the beginning. None whatsoever. It was my wife sitting across a table from me, with tables of words from the Adult Cochlear Implant Home-Based Auditory Training Manual Postlingual Hearing Loss available here. My good ear was covered with an earplug & headphone with white noise. Using the cochlear side only and looking away from her lips, I would listen to my wife who would read single words & say it back to her. She would show me the word if I got it wrong, and repeat the sound until I brain trained that word. This took us about 30-60 minutes per day, and we had planned this from before the surgery date by reducing my work hours to allow for this.
At the beginning, I got 0% correct. Gradually, this improved. I still can’t tell the different between M & N sounds in single words, and certain vowel sounds, but they work in a sentence context.
Later, we moved to pitch recognition using a piano. It was hopeless, until I had a hybrid component placed to use the residual low pitch hearing. That was great for a month or so, until that residual hearing suddenly disappeared. Lost all pitch recognition again now, despite further training & trying. Never mind, got the good ear still & as a result of not using the hybrid processor, the device is much simpler to manage.
I started streaming podcasts a couple of months later & it was hard. Now, I’m up to streaming certain podcasts at 150% speed (which I would normally listen to at 200% speed), but other podcasts which use background music behind the speech are at 100% speed or impossible. British, American, Australian, Scottish accents are fine. General African & Middle Eastern accents are very hard for me to understand. Irish accents I can’t even understand using my good ear!
Overall, it’s been a win. Hearing is not perfect; far from it! But it makes hearing easier than not having it, and prepares me in case the other ear ever decides to take a permanent holiday too. I’ve come to accept that I’ll never use the cochlear ear to listen to Rachmaninov again as the nuances of any classical music is impossible. Perhaps some rap might work, if I ever get into that!