You might try again, or maybe if you haven't tried already, sign out of your IFTTT account and sign back in again. If that doesn't resolve the issue, try disconnecting your HE hub from your IFTTT account and reconnect.
This is a common IFTTT issue I've experienced with various services. Most frequently Logitech Harmony, but I know from experience that no manufacturer is immune to the issue. Typically disconnect and reconnect resolves the issue.
Having said that, as @ogiewon mentioned, you will only see devices that are valid for a particular action or trigger.
Currently, I'm not experiencing an issue. So while it could be due to a partial outage as @bobbyD was saying, it could also be an isolated incident within your IFTTT account.