The OP should go down a checklist that includes the following:
Is the niche kw a buying keyword? Does it naturally relate to people about to buy something to solve an urgent problem, or just to get free info?
Is server's loading okay? Does it provide good uptime? Is the loading problem on the client's side (bad web design)?
Is the affiliate product/offer/service decent? Is the site preselling it well? Is the landing page good?
If adsense, does the keyword have high or low PPC competition? If low, that often means it's not highly clicked on.
Is the monetizing link, or ad placement optimal? Is the site too ugly to keep retain visitors, or too pretty for visitors to leave via clicking the link?
That kind of thing.