See: Use of "have had" , "had had", "has had" .
It had been done before implies a singularity and recency (present perfect tense), but it has been done before is plural and past tense (past perfect tense). [Implies means not critical but assumed, the recency is required and not implied for it to be had].
If there were a recent prior attempt (possibly multiple recent ones) then "it had been done before", but if it was done some time ago or multiple times (not recently) then "it has been done before".
By changing "had" to "had not" (hadn't) it is a negation of the above. The negation cancels the recency by imposing never upon the circumstances. So "has not" is that you are described by others as someone who didn't but "have not" is that you don't, as claimed by yourself or others ("I have not", "You have not", or third person singular "He has not" (talking like you are excluded from the conversation either by physical distance, or close up might be rudeness or lacking inclusiveness (shutting you out of the decision)).
That causes "has" to refer only to a third person, a "present perfect tense with a third person singular subject". Examples: "I or you have eaten", "I or you have not eaten", "He or she has eaten", but "They have eaten" or "They have not eaten".