It may be that your browser is still caching parts of the old application.
We recommend that all users immediately clear their browser cache after upgrading any of our web-based applications so that you can be sure that none of the old stylesheets or other program elements is still being used by the browser.
There are two options to check that:
1) Try using one of the browsers in "Private" (Edge) or "Incognito" (Chrome) mode, some extension/plugin may interfere with the SpiraPlan operation and prevents it from normal operation, so
2) Check the output of browser console messages for errors (F12) when you see the issue.
Please send support a screenshot of the console messages.
If the issue keeps unresolved, please log a support ticket, including the Event log records and screenshots as evidence.