Voicemails are linked to a gallery and must be enabled from there.
Here's how to enable Voicemails for a gallery:
Open the gallery where you want to collect voicemails
Click the Menu button at the top right (the purple circle with 3 white lines)
Scroll down and select "Voicemail Settings" on the menu list
Toggle on "Enable Voicemail"
Set a custom greeting message. We use a default greeting if you don't set one.
Save Changes
This enables voicemails in the guest portal. Guests accessing the gallery will see a Voicemail button on the menu bar. When clicked, they'll be taken to the call screen, where they'll hear a greeting message before leaving their message.