I have tested this on a Smart Drive 61-D LMT and get the same error on any of the voices I try.

Butter is correct about this.

What you could try and I do not know if it would work is to replace voice Jack with an older voice Jack and see if it will work on your Drive 51.

If it works then you can edit it and then try again.

But make backups of what ever you try.

You will need an older GPS say the 2595 to get the older version of the TTS voices.