In some cases, you will need to changes the network settings on your PS4.
1. Open settings of PlayStation
2. Go to your 'Network settings'
3. Select 'Set up an Internet connection'
4. Then select 'Use WiFi' or 'Use a LAN cable' based on your connection
5. You'll be able to see an option of 'Custom'
6. Choose the 'Custom' option and then select your network
7. You'll be routed to IP address settings. Select "Automatic" in the IP address settings
8. Next, you can see a page of DHCP Hostname and you can choose "Do Not Specify"
9. Upon selecting 'Do Not Specify', you'll be moved to the page of DNS settings and you need to choose 'Manual' option.
10. You'll get an option to enter Primary and secondary DNS. Enter the following: Primary DNS: 8.8.8.8 Secondary DNS: 8.8.4.4
11. Next, you can see the MTU settings options and you need to select 'Manual' over here as well. Enter: 1473
12. At last, you can choose an option of "Do not use" proxy server. After this is updated Test your network connection. Once the testing is finished and everything is successful you can relaunch the game and check for the voice chat.
If the voice chat doesn't work after applying the changes, please check with out ISP since some ISP’s DNS servers have difficulties resolving the Internet names of the voice chat servers.