Slack integration doesn't recognize any slack channels

I set up the slack integration per the sentry guide. It connected to slack, I added the sentry app to my channels (even though it is a public channel I’m trying to access) but when I try to add a rule, I keep getting the error "The slack resource “{name of channel}” does not exist or has not been granted access in the Slack workspace.
I’ve seen a lot of threads about people getting this with private channels, but I’ve tried multiple public workspaces and a private one and no luck.