So apparently it fixed itself? I guess I'll close this now...
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I recently had the same issue on VCSA - after joining the PSC to AD domain and rebooting, I received an identical HTTP Status 500 error page.
It looks like it is a cookie issue, so opening a "private" browser (private/inprivate/incognito/etc...) with no cookies will resolve your issue immediately, or close/re-open browser or clear browser cookie(s) should also resolve the issue.
Tip: In Chrome, clicking on the "Secure" text in URL bar will show details about connection, clicking on the "x in use" link under Cookies will display the current page's cookies and let you view or remove them. The cookies I had all said "Expires: When the browsing session ends".
Specifically, clearing/removing the JSESSIONID cookie and reloading the page will create a new session.