Might be a long shot, but GRCs Spinrite has saved a couple drives of mine. It won't work if there's a problem with the physical connection to the drive but almost everything else it can fix (at least momentarily) and actually grants a nice speed boost in the process for drives that have gotten too messy.
Aside from all the flashy handwavy marketing "technospeak" what SpinRite actually does under the hood is re-read each bit from the disk thousands of times and then see if it gets more 0s or 1s.
It works well when a drive is past the point where its internal error correction code no longer works, but you just want to beat the right answer out of it with a baseball bat.
These days professional disk recovery by a lab is sub-$1000 and they recommend not using brute force tools like Spinrite because it can also exacerbate the problem before they get hands on it.
