There's an announcement on the main page:

As announced, we are currently implementing the login limitation so we can monitor the optimization of the Duty Finder more precisely. We will be releasing the limitation as we go along, so we please ask for your patience.

We apologize for the inconvenience that this is causing everyone, but we please ask for continued cooperation for an overall stable environment.
Sounds like the 1017 error might be them deliberately throttling the population limit in order to solve the duty finder problem. Give it a couple of hours. MMOs rarely have smooth launches, just be patient and try to be as helpful as possible when reporting bugs if you want things to get back on track as quickly as possible.