Pain after dental implant

My dad had an implant placed in the upper jaw, and after six months, a dental model was made and fitted. However, since it was a tooth without any special precautions, he was told that there might be pain when chewing initially, so he was advised to start with soft foods to get used to it. But the adaptation period has now exceeded a year, and he can't chew on that side at all. We've asked the clinic several times, but they only adjust the implant head and tell us to wait, without offering any further solutions. My dad is very frustrated... Do you think it would be better to seek a consultation at another hospital?