I've drastically changed niches and continue to get denied by the companies I now want to work with. Is making contact with an AM a good start? It seems like CJ isn't as welcoming or AM friendly as other networks are.
You can't get an AM at CJ until you're a CJP (minimum 3 months of $10,000 commissions, and an approval process). Contact each advertiser directly regarding why you're denied - use the CJ mail function, or email the merchant directly using the email address on their detail page.