Can't Open UI designer

I was guided by Q & A answerer to post here.

After the installation of Bonita Studio Community and Bonita Platform in reference to the document, I started Bonita Studio and Bonita Platform(Of course configured environment variable JRE_HOME).
They worked well.
Then, I made a new diagram and pushed "Open UI designer" button, but the browser displayed "404."

This trouble looks same to the one on the Bonita documentation, but ui-designer.log is a little bit different.
For example, in ui-designer.2021-02-15.log, there are "Unhandled exception"(line 15) and "500 Internal Server Error"(line 19),
and in .log, "Failed to post on ..." (line 6113) and "Not Found (404) - The server has not found anything matching the request URI"(line 6177).