We’ve made some fixes. You can use this fixed version:
https://github.com/CleanTalk/wordpress-antispam/releases/download/dev-version/cleantalk-spam-protect.zip
1. Go to WordPress Administrator Panel —> Plugins.
2. Find the plugin “Spam Protection by CleanTalk” —> Deactivate.
3. After the automatic page refreshing find the plugin again “Spam Protection by CleanTalk” —> Delete. Confirm “Yes, delete these files”.
4. Download the plugin archive from the link.
5. Go to Plugins —> Add New —> Upload Plugin.
6. Choose the downloaded archive and press “Install Now”.
7. After the installation, activate the plugin, make sure that the access key matches the key from your CleanTalk Control Panel.