Are your co-workers ignoring you? Welcome to my world! In your case, however, that is probably because Slack is currently down (as of about 11AM EST). According to its status page, some workspaces are experiencing issues with messages sending and loading.
We're receiving reports about issues with messages sending and loading. Our team is on the case and we'll report back once we have an update to share. https://t.co/ZstseqpFlL
Slack outage notice
We will update this post once the Slack outage is over.