'No one has ever succeeded in providing conclusive evidence for the claims of astrology; therefore we must conclude that astrology is nonsense.' Which fallacy is committed in the above argument?

The argument turns the lack of proof into proof of the opposite.

No one has provided conclusive evidence for the claims of astrology.

From this absence of proof it concludes that astrology is nonsense.

Failing to prove a claim does not by itself establish that the claim is false.

Inferring falsity purely from want of evidence is the appeal to ignorance.