Blank panel after upgrading to Kirby 3.6.0

Hi there! I just upgraded my site to Kirby 3.6.0 and the frontend is working fine, however I get a blank page when trying to visit the panel. The console error message reads:

DOMException: Failed to execute 'pushState' on 'History': A history state object with URL 'http://localhost:35411/panel/site' cannot be created in a document with origin 'http://localhost:8080' and URL 'http://localhost:8080/panel/site'.

    at Object.setState (http://localhost:8080/media/panel/84e399b8f2181ccd73394fdeddff1638/js/index.js:1:14524)
    at Object.init (http://localhost:8080/media/panel/84e399b8f2181ccd73394fdeddff1638/js/index.js:1:12871)
    at a.created (http://localhost:8080/media/panel/84e399b8f2181ccd73394fdeddff1638/js/index.js:1:14845)
    at Vt (http://localhost:8080/media/panel/84e399b8f2181ccd73394fdeddff1638/js/vendor.js:6:11291)
    at nn (http://localhost:8080/media/panel/84e399b8f2181ccd73394fdeddff1638/js/vendor.js:6:25303)
    at a.Cn._init (http://localhost:8080/media/panel/84e399b8f2181ccd73394fdeddff1638/js/vendor.js:6:32894)
    at new a (http://localhost:8080/media/panel/84e399b8f2181ccd73394fdeddff1638/js/vendor.js:6:30461)
    at http://localhost:8080/media/panel/84e399b8f2181ccd73394fdeddff1638/js/vendor.js:6:19454
    at init (http://localhost:8080/media/panel/84e399b8f2181ccd73394fdeddff1638/js/vendor.js:6:19485)
    at http://localhost:8080/media/panel/84e399b8f2181ccd73394fdeddff1638/js/vendor.js:6:56812

Am unfortunately not skilled enough to know how to read this and what to do. Any pointers? Thanks in advance!

[fabianmichael]

I also had a blank screen issue on an IONOS webspace. It was caused when history.pushState() tried to push the non-ww URL of the website as path, while the panel loaded from the www-version. At IONOS, SERVER_NAME is set to the domain without www prefix, but HTTP_HOST contains www. I was able to fix that temporarely by adding the following line to my index.php file before loading anything else:

$_SERVER['SERVER_NAME'] = $_SERVER['HTTP_HOST'];

[arnaudjuracek]

In my setup the blank panel was due to a port mismatch, and was solved by using this index.php :

<?php

require __DIR__ . '/kirby/bootstrap.php';

// Fix blank panel on Kirby 3.6.2 with kirby-webpack
if (($_SERVER['HTTP_X_FORWARDED_FOR'] ?? null) === 'webpack') {
  $_SERVER['SERVER_PORT'] = 8080;
}

echo (new Kirby)->render();

Where 8080 is the matching port of your BrowserSync options.