Interestingly, I decided to try this from a softphone as you did in the video. Guess what? It worked as expected. I was able to dial *43 for an echo test and could hear the recording with instructions with no problem. However, it still will not work using our desktop SIP phones. For reference, I am using Yealink T48G and T46G phones.
Rob - I would be curious if you could retest using one of your desktop phones...