Their status message says 100% uptime so this inability to read or send messages is all our imagination!<p>Eventually if enough people notice they'll put an ! on their status page (as they've done for "Android users can't log in"), and then remove it from the browseable history in a few weeks.
At this point their 99.99% SLA is a total joke, make sure to claim your service credits <a href="https://slack.com/terms/service-level-agreement" rel="nofollow noreferrer">https://slack.com/terms/service-level-agreement</a>