I got this error when I approved the request from Ezoic. I do have an existing Adsense account, but I don't have an Ad Manager Account. Later, I tried sending the invitation again after selecting that I have an AdSense account, and now the requests aren't even opening. I keep getting the error We apologize for the inconvenience, but we are unable to process your request at this time. Our engineers have been notified of this problem and will work to resolve it.
I even tried changing my email to solve the issue, but still the invitation is going to the initial email. I'll appreciate if I'm able to signup using the primary email itself, but incase that's not possible please use my secondary email for the activation.