Sorry but this is not how the plugin is described in the Codex
https://simple-press.com/documentation/codex/plugins/our-plugins/available-plugins/polls/
Click the check box to the left of “Allow poll results to be hidden” to select this option. This gives the poll creator a choice of whether or not to hide the poll results until the poll expires. After the poll expires, the results are visible in the post.
So each new poll must have an option, to be decided by its starter, either to make results hidden or not.
And this is what context Help says:
Also, you can choose to allow polls results to be hidden until the poll is closed. If this option is enabled, when creating a poll, users will be able to have the results hidden until the poll is closed.