Starting June 28th, you will no longer be able to log in to a Curse account that was not merged with a Twitch account. If you have not yet merged your Curse account with a Twitch account, please do so here! Otherwise, your account and its content will be inaccessible.
I'm afraid I cannot tell you much on the silence, however, you will want to submit a ticket if you are looking appeal or any further information. I do also recommend you check any spam or trash folders you have in case the email was routed there.