Thank Oliver for the advice. Since I have the same problem as Ulrike, I copied the error msg from the console. Here is what I got:
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[Error] Failed to load resource: the server responded with a status of 404 () (cm-resource-selector.min.js.map, line 0)
[Error] Failed to load resource: the server responded with a status of 404 () (image.php, line 0)
[Error] Failed to load resource: the server responded with a status of 404 () (icon.svg, line 0)
[Error] Failed to load resource: the server responded with a status of 404 () (icon.svg, line 0)
[Error] Failed to load resource: the server responded with a status of 404 () (icon.svg, line 0)
[Error] Failed to load resource: the server responded with a status of 404 () (icon.svg, line 0)
[Error] Failed to load resource: the server responded with a status of 404 () (icon.svg, line 0)
[Error] Failed to load resource: the server responded with a status of 404 () (icon.svg, line 0)
[Error] Failed to load resource: the server responded with a status of 404 () (icon.svg, line 0)
[Error] Failed to load resource: the server responded with a status of 404 () (icon.svg, line 0)
[Error] Failed to load resource: the server responded with a status of 404 () (icon.svg, line 0)
[Error] Failed to load resource: the server responded with a status of 404 () (icon.svg, line 0)
[Error] Failed to load resource: the server responded with a status of 404 () (icon.svg, line 0)
[Error] Failed to load resource: the server responded with a status of 404 () (icon.svg, line 0)
[Error] Failed to load resource: the server responded with a status of 404 () (icon.svg, line 0)
[Error] Failed to load resource: the server responded with a status of 404 () (icon.svg, line 0)
[Error] Failed to load resource: the server responded with a status of 404 () (icon.svg, line 0)
[Error] Failed to load resource: the server responded with a status of 404 () (icon.svg, line 0)
[Error] Failed to load resource: the server responded with a status of 404 () (icon.svg, line 0)
[Error] Failed to load resource: the server responded with a status of 404 () (icon.svg, line 0)
[Error] Failed to load resource: the server responded with a status of 404 () (icon.svg, line 0)
[Error] Failed to load resource: the server responded with a status of 404 () (icon.svg, line 0)
[Error] Failed to load resource: the server responded with a status of 404 () (icon.svg, line 0)
[Error] Failed to load resource: the server responded with a status of 404 () (icon.svg, line 0)
[Error] Failed to load resource: the server responded with a status of 404 () (icon.svg, line 0)
[Error] Failed to load resource: the server responded with a status of 404 () (icon.svg, line 0)
[Error] Failed to load resource: the server responded with a status of 404 () (icon.svg, line 0)
[Error] Failed to load resource: the server responded with a status of 404 () (icon.svg, line 0)
[Error] Error: Env not inited yet
[Error] Failed to load resource: the server responded with a status of 404 () (h5p-show-when.js, line 0)
[Error] Failed to load resource: the server responded with a status of 404 () (h5p-show-when.
css, line 0)
[Error] Failed to load resource: the server responded with a status of 404 () (radio-group.js, line 0)
[Error] Error while loading script – Event {isTrusted: true, type: "error", target: