Discourse uses the max new accounts per registration ip Site Setting to limit the number of accounts that can be created from a single IP address that has no Trust Level 2 or higher users associated with it. The setting has a default value of 3 users.
If you would like to allow more than 3 users to register from an IP Address, you can either increase the max new accounts per registration ip Site Setting for all IP Addresses, or you can add the specific IP Address to the Screened IPs list.
The Screened IPs list is found at Admin / Logs / Screened IPs. To allow an IP address, enter it in the New field, select ‘Allow’ from the dropdown menu, and then click the Add button:
