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.
We're aware of this issue and actively working to address it. The 'Beta Bucks' (currency-based) auction house will be unavailable until this issue is resolve, resulting in one or more errors when attempting to use it. The gold auction house is however currently unaffected.