Clear your browser cache
A simple first step is to clear your browser cache and/or try a different browser. If the issue is restricted to a single browser, be sure to clear all of the cached files, then restart the application.
Replace your TinyMCE folder
TinyMCE is the HTML Editor WordPress uses to power its post and page editing features. The TinyMCE files may have become corrupted during a WordPress upgrade. If you experience the issue shortly after upgrading, download a fresh copy of WordPress and replace the /wp-includes/js/tinymce/ folder on your server.
For more help, or to ask a question, please open a support ticket from your HostPapa Dashboard. Follow this link to learn how.