Exiting voicemail to IVR doesn't work

Having an issue similar to this IVR - go back to IVR after leaving voicemail?

I am having an issue where a caller dials an extension, and the user doesn’t answer. The caller dials 0 to get back to the IVR, but the options on the IVR don’t work, and the caller cannot dial another user’s extension.

The return to IVR option in the IVR are set.

Any ideas?