Thanks for posting. Upgrading to 6.8.4 shouldn't be a problem.
Could you please give us some more information about your current setup. If you go to "Forum > Toolbox > Environment" in WP-admin, could you please copy that information and post here please.
That's unfortunate. Could you try going to "Tools -> Site Health" and click the second tab "Info" and then click the button "Copy site info to clipboard" and paste here, or e-mail it to email@example.com if you prefer. We really need to know your wp version and what version of simplepress you are using and other plugins that might interfere.