I just adopted an old African grey that has had a rough go of it throughout her life including a foot amputation. Her "good" foot cannot perch, it is always flat. Is this just a matter of atrophy? Is it something I can help her strengthen?
If you need help finding an avian certified vet, we can try to help if you provide a general location. A regular or exotics vet will not know what to do about this. If you are comfortable sharing a general proximity and are willing to drive an hour or so, people will try to help you find one.
It's impossible to know what the problem is without really careful and informed investigation (likely, including blood work, possible vitamin panels, x rays etc). Certain viruses can also lead to lameness...could be arthritis, could be an infection, could be neurological...you just need more info . Birds should get blood work at minimum every 3 years (more often if needed)
You can call these vets and ask if they are certified avian-- if none are and you search without much luck, you could try an exotics vet with a good reputation among parrot people, but it's worth a drive to see an avian vet. Just because a vet deals with birds does not mean they are avian certified.