There is an admin setting that lets gives domains the ability to shut bots off. If you can access Chat, but no bots show up when you search in the search bar in the top left, the admin may have disabled bots.
To find out whether bots are enabled for your team's Chat, try searching/adding for other bots such as Giphy, Wrike, or Streak. If you're experiencing the same issues, then it's likely that bots are disabled for your team.
For more information on how to change this setting, visit Google's help documentation on Bots.
If you tried something like
@polly "Your poll in quotes" "voting option" "another voting option" but nothing is happening, then you’re likely not tagging Polly correctly. In Hangouts Chat, you need to hit tab after typing @polly or selecting Polly by clicking on it in order for us to recognize the mention.
If you continue your poll question without selecting Polly, the @Polly will appear to be text and not an @mention.
Notice how if you select Polly by hitting tab or clicking on Polly, then the @polly auto-capitalizes to @Polly.