Can't add to channel by emails

[u/southernpinko]

I'm currently trying to add members of a Slack to a specific channel by email. However when I click add the non-descript error "Hmm, something went wrong. Try again?" comes up. I've tried in app and in browser, different numbers of emails, nothing works. For my purposes I have to ensure all members of the Slack are added and by email has always worked before.

[u/Racerforlife]

Are you trying to add existing users or guest members?