As some have surmised, iNaturalist is back up. However, there may be some bugs and other minor issues so please go easy on it for another hour or two. If you can consistently find any bugs, please fill out a new topic in #bug-reports and include details.
Thanks for your patience, everyone, and we again apologize for the extended outage.
EDIT: please don’t fill out any bug reports about notifications just yet, we know there are some issues with them.