Hello @grudesky,
PowerPress saves the error message to the database’s options table. When it displays the message it then deletes it from the database. For what ever reason the user you are signed in as must not be able to delete this database record, either because of permissions or because of some other error. The fact that your WordPress site cannot delete the record may indicate an issue where you do not have permission to delete records. You will want this fixed or at minimum find out why this is happening.
One quick google search indicated that it coudl be that the database tables are damaged and running REPAIR and OPTIMIZE on the tables may fix the problem, while another solution (if you are using a caching plugin) was to clear the cache, or restart Apache to clear any caching that may be happening with PHP.
You can go into phpmyadmin and manually delete the value. You must find your options table for your WordPress site. In a normal installation it is “wp_options”. in this database, search for the key name “powerpress_errors”. When you find this record, simply delete it and it should make the error go away. If you do not find the record, then it’s definitely something to do with caching.
Please let me know what you find out.