Addon Button will appear after several minutes

Hello everybody,

the Menu Button Addon is not present at the start of the paper UI. (see screenshot)
Only when I reload the page a few times do I get the menu item.
For every update, the error 404 - Not found in the lower right corner comes
Can someone help me please?

many Greetings,

System setup?

Windows 10 64 bit

Openhab version, Java version, please
Browser used

You haven’t given us much to go on

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Have you updated to 2.4 yet?