Are you in creative mode?

> Wolves will only remain angry as long as they have something to attack. Summoning an angry wolf will immediately make it non-angry since it doesn't have a target.

[Source.][1]


  [1]: https://bugs.mojang.com/browse/MC-33558?focusedCommentId=182218&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-182218