You could try uninstalling WordPerfect, then re-installing it. It's also possible a recent Windows update or a spyware infection is causing the problem.
BUT... I humbly suggest abandoning (uninstalling) WP, and installing free, safe, open-source
OpenOffice to replace all other word processors/office suites on the planet. It can convert, read, or save most any document type (even more than Microsoft Word), and in my 20-year experience is much better than anything Microsoft or WordPerfect has ever produced. Did I mention it is free? It is a favorite of computer professionals and students.