Can't clear cache, site permissions

Can't clear Hummingbird's Page Cache. The message shown:
There was an error during the cache purge. Check file permissions are 755 for /wp-content/wphb-cache or delete directory manually.

- Security plugins were deactivated
- wp-content and wphb-cache folders have 775 folder permissions set
- define( 'WP_CACHE', true ); was added in the wp-config.php file