Media and plugin upload button not working

After the WP 5.5.1 update the Media upload button and the plugin upload button will not work. I have tried to turn off all plugins, but it doesn’t help. I have also installed the Jquery Imigrate Helper, but that didn’t help either. I have tried from both Safari and Chrome. The error message when trying to upload a jpg through the different uploading methods says: “Unexpected response from server. The file may have been uploaded successfully. Check in the media library or reload the page.” (translated from Norwegian)
Please help me!