[JavaScript Error: "Component returned failure code: 0x804b000a (NS_ERROR_MALFORMED_URI) [nsIIOService.newURI]" {file: "chrome://zotero/content/xpcom/storage/webdav.js" line: 205}]

Are there non-alphanumeric characters in your WebDAV URL, username, or password?

See this thread for how you can experiment to see what characters are causing this error, and please return to this thread and let us know the results:

https://forums.zotero.org/discussion/comment/419796/#Comment_419796