Is the usage Could not be able to correct?

Answer 1

The construction is redundant: "Could not" means the same as "not able to."

You might use the form "would not be able to" or simply "could not" or "cannot" which are all roughly the same with some connotations that vary by tense.

Note that "could not" is the past tense but also colloquially used to say "will not be able to" in the future. All of these mean that something "cannot" be done (impossible), but in many cases it is a choice not to act. You should correctly use "may not" when something is prohibited, or "will not" when it is your choice not to.

Answer 2

The phrase "could not be able to" is redundant. It is more concise to simply say "could not correct" or "was unable to correct."