Is money earned from a previous commission (9 months ago) permissible or impermissible, if it later becomes clear that there were Sharia-related concerns on the website after a new review?

There is no harm for the questioner in taking a commission for bringing a client, because he did what was within his capacity and investigated to ensure the site was free of religious prohibitions. What is considered for the permissibility of the commission is that the original activity of the site be permissible, even if there is a slight transgression in one of its sections, such as discussing a gambling place or displaying an uncovered image, which has become a widespread affliction.