To create a notification:

1- Navigate to Notifications > Add New.
2- Add your title and the content.
3- You can change the Notification layout and it’s styles from the notification options meta box. (Examples: layout1, layout2, layout3 and layout4).
– If you can’t see the previous notifications examples, it means you have clicked on the X button to close it and to see it again, open your browser console Ctrl+Shift+J or Cmd+Shift+J on a Mac and navigate to Application > Cookies and delete plume_core_notification_XXXX_cookie cookie where XXXX is a number.
4- Publish your notification.

– Navigate to Plume Core > General > Notifications and select the notifications you would like to appear to your website visitors.

– You can set the Expire days to a number of days, so the notification will appear again after the Expire days you have entered.

– You can set the Appear after to a number (seconds) and it means the Notification will appear after the page is loaded (in seconds).

If for some reason the notifications slug has a conflict with other plugins, you can change the slug from Plume Core options > Notifications > Slugs.

Navigate to Plume Core options > Notifications > Slugs and change the main slug notification-items to anything else that doesn’t has a conflict.

http://plume.graphicfort.com/notification-items/notifications-layout-1/

The notification-items is used for the notification slugs and you have activated a plugin that uses notification-items as a slug, so you will need to change notification-items to anything else.

EX:

http://plume.graphicfort.com/notification-posts/notifications-layout-1/

after that you will have to navigate to Settings (From the WordPress admin left bar) > Permalinks and click on save button.