My options don't save. How can I fix that?
If your Wordfence options aren't saving a first thing you want to try is to update Wordfence. If you change your API key this should fix any "cron key" errors you're having.
If you find any errors here you can try disabling all plugins except Wordfence and swap to a default WordPress theme and see if you are then able to save your options. If that doesn't work, take a screenshot of the errors you get in the browser console. Share that screenshot together with a detailed description of your issue with the support staff in WordPress Wordfence support forums.
You also might want to check your database to verify that the Wordfence configuration table exists and is not corrupt. Log in to view your database via for example phpMyAdmin. Verify that there are several tables named according to this pattern [your prefix]_wf[tablename]. The specific table you are looking for is wfConfig. If your WordPress database prefix is wp_ that would mean your Wordfence config table is called wp_wfConfig.
If you can't find any tables in your database that match the description above your WordPress user might not have permissions to create tables in the database.
Additionally, make sure that your database user has the "ALTER" privilege, so that database tables can be modified when necessary. You can confirm this near the top of the Wordfence Diagnostics tab on the Tools page of the Wordfence menu.