I would not say it's accurate to say FX-322 "does not work" in humans. Firstly, it is shown that the treatment only penetrates the cochlea to cells responsible for transduction from 12 - 20 kHz. There is very little (well, less) 'important' spectral content at those frequencies for humans, especially when it pertains to speech. With regards to speech, past 12 kHz, you are mainly dealing with lower amplitude harmonics of upper-frequency consonant sounds like "f," "th," "s". One thing to note, is virtually all adults past the age of 30-40 already have some significant hearing loss past 12 kHz anyway, meaning that "normal adult" hearing in those regions is already damaged to a certain extent yet normal adults usually don't have any issues with intelligibility, chronic tinnitus etc.
The Frequency Therapeutics studies did show statistical improvements in speech intelligibility, which was virtually the only thing tested and is almost certainly what was to be expected due to the limited bandwidth of what the treatment targets and what that would translate to in terms of audibility. Those that do not really understand the implications of these reported outcomes lost confidence in the company, which was evidenced by the stock tumbling and people claiming it did not restore hearing. As a medical and drug researcher, musician and avid audiophile, I find the "poor" results of FX-322 and Frequency Therapeutics as a whole still very hopeful. FX-345 is expected to penetrate deep enough to treat 4 kHz - 20 kHz, which not only encompasses the region treated by FX-322 but also the significantly more important audiometric region of 4-8 kHz, which I believe would be optimistically predicted to show significant improvement 99%+ of hearing loss cases. Being able to treat tinnitus itself is perhaps not as guaranteed, but most cases of tinnitus are a result or at least highly correlated with some sort of measurable hearing losses or damage, so I don't doubt that a restoration of hearing combined with time for the plasticity of the brain to do its thing will help a massive amount of people, especially those that are on the younger side.
Personally, a majority of my hearing loss and the frequency of my tinnitus is contained in the midrange at 500-1500 Hz, which is probably the worst place anyone could hope to experience a narrower-band loss. It also means that as it stands, both FX-322 and FX-345 will do very little for me since my damage is under 4 kHz. Despite this, I've still invested quite a bit of money into the company, because even if it does not help me, I am that confident in its success. If outcomes of FX-345 are a success audiometrically, I'm confident the company will probably explode overnight and it is very likely a further formulation to treat the whole cochlea will be developed.