What happened:
Back in July 2017, Tapatalk acquired Zetaboards and zIFBoards (formerly InvisionFree) which ORP was hosted on. Following the acquisition, all hosted boards were scheduled to be migrated to a new forum software: Either ZetaBoards or TapaTalk.
They started rolling out these changes a few months ago, prompting admins to choose between ZetaBoards or TapaTalk. The exact options looked like this:

ZR reported that he received a notification a while ago. He had the choices shown on the screenshot. Note that a migration will definitely happen at some point. For now, he chose to defer the change.
If admins didn't respond to that notification, a migration to TT was automatically started without notice. This is what happened with ORP yesterday.
Most likely, Jigebren and TheMeAndMe were the only admins who got notified. However, they've both been inactive for years.
The change sadly can't be reverted. The only option would be to talk to the TapaTalk support to manually switch the software to ZetaBoards which is at least somewhat similar to the old InvisionFree boards.
If you're looking for a place that feels like the old ORP, you're welcome to stay and make yourself comfortable. More importantly, this forum is self-hosted and not in the hands of a big corporation.