We recently migrated to RingCentral and have come to discover that one of the biggest features we use is not available with RingCentral. From our desk phones, we are unable to conference if the two calls we want to conference are both external. It gives a busy signal instantly.
To clarify, if we call an external phone number, then try to conference with a second external number, this does not work. However, if we call an internal extension, and then try to conference an external phone number, that works fine. If we call an external number and conference and internal number, that also works. Lastly, if we call an internal number and try to conference a second internal number, that works as well. It only fails for trying to conference two external calls.
This works fine in the app, but it is a limitation on the desk phones. We reached out to support and were told that this is a limitation for all desk phones, regardless of model. However, in case it helps, we all have Mitel 6940 IP Phones.