Why is my voicemail no longer working?

The voicemail settings are controlled by the carrier, so call your carrier.

Have you turn On your voicemail?

An example how it works with my carrier:

Call 12331 to turn On.

Call 12330 to turn Off.

Call my voicemail box xxxx and press 11 for the main menu. Choose 2 for the personal settings of your voicemail. Choose 3 for PIN code and choose a 4 digit code.

You can also change your pin code here and indicate when your voicemail should ask for the pin code.

FYI: if you enter an incorrect code 3 times and you will receive a temporary code via SMS. You can change that later.

When I get a voicemail, I get a sms message from my carrier.

Contact your cellular carrier. That's a carrier feature.

If you want to listen to your voicemail, go to Phone and call your Voicemail box.

Or do you mean the Voicemail icon at the bottom right of the screen?