Title: Invalid header error during activation
Last modified: April 15, 2022

---

# Invalid header error during activation

 *  [organicsulfur4health](https://wordpress.org/support/users/organicsulfur4health/)
 * (@organicsulfur4health)
 * [4 years, 2 months ago](https://wordpress.org/support/topic/invalid-header-error-during-activation/)
 * Unable to activate plugin. I get an invalid header error message when doing so.
   I suspect it’s because the plugin has not been updated to be compatible with 
   WordPress 5.9.3, which I run on my website.

The topic ‘Invalid header error during activation’ is closed to new replies.

 * ![](https://ps.w.org/spreaker-shortcode/assets/icon-128x128.png?rev=1056731)
 * [Spreaker Shortcode](https://wordpress.org/plugins/spreaker-shortcode/)
 * [Support Threads](https://wordpress.org/support/plugin/spreaker-shortcode/)
 * [Active Topics](https://wordpress.org/support/plugin/spreaker-shortcode/active/)
 * [Unresolved Topics](https://wordpress.org/support/plugin/spreaker-shortcode/unresolved/)
 * [Reviews](https://wordpress.org/support/plugin/spreaker-shortcode/reviews/)

 * 0 replies
 * 1 participant
 * Last reply from: [organicsulfur4health](https://wordpress.org/support/users/organicsulfur4health/)
 * Last activity: [4 years, 2 months ago](https://wordpress.org/support/topic/invalid-header-error-during-activation/)