Why can't I add new sources of income to Payoneer?

I am asking the question here for I contacted several times Payoneer support but in vain, no answer. I would like to add a new source of income, but whenever I try to, I receive a notification saying that I cannot link Payoneer to this account and that I should register with another address email. So, why am I facing this issue? Is it because my balance is low or my account is no longer working?
Thanks!