This information is no longer valid starting with the release of 04/13/2023
All Jira Service Mangement users (except anonymous users) can vote.
Customers’ Voice is based on Forge and therefore comes with many advantages but also some disadvantages.
Within Jira Service Mangement you can enable your customers for your Customer Portal in two ways:
On this page you can find detailed information about this topic:
During the release of Forge for Jira Service Mangement, Atlassian announced the following.
"...In a later release, we plan ... the ability for anonymous users (users not logged in with an Atlassian ID) to initiate requests through the service portal..."
(Source: https://community.developer.atlassian.com/t/forge-is-now-available-for-jira-service-management/56543 )
Customers with a Portal-only account cannot access Customers' Voice through this restriction
Here is described how to convert a Portal-only account into an Atlassian account.
Please vote for this ticket https://ecosystem.atlassian.net/browse/FRGE-189 and also write a comment that you need this functionality.