I know this web app doesn’t work with some shared hostings, because of the server configuration but I’m not sure how is the shared hosting’s configuration.
You can try to add the following rewrite rules to .htaccess
RewriteRule .* - [E=REMOTE_USER:%{HTTP:Authorization}]
RewriteCond %{REQUEST_URI} !^/admin/
if it doesn’t work, try this again.
RewriteRule .* - [E=HTTP_AUTHORIZATION:%{HTTP:Authorization}]
After you added, please clear the browser cache before you refresh the page.