There are a several reasons your 500px may be blocked because of "Too Many Requests"
1. You made too many unsuccessful attempts logging into your account.
2. You could be following and unfollowing too many members too quickly.
3. You are liking too many photos too quickly.
Our moderation system generally detects this activity as some sort of spam type behaviour on your account and this detection is in place to minimize accounts created for spam and abuse of the site's features for self-promotion. Although we understand this may not have been your intention, we are unable to remove the "Too Many Requests" block manually.
How long will you be blocked?
Once this block has been placed on your account, access to your account via web will not be possible for 1 hour. Once this hour is up, you'll be able to continue using your account to it's fullest.
How else can you access your account
In the meantime, you can use the mobile version of 500px to continue your daily activity! If you do not have access to the app, tethering or VPN on web will help get you going again!