There seem to be some issues at Kobo Server https://kc.kobotoolbox.org
The server seem to not accepting the submissions for data for last 2 days.
Please look into it and resolve as soon as possible. Find below the screenshot.
@Kal_Lam The server settings are correct. This issue started since yesterday. Before that it was uploading the data from the same user. It would be great if you can reverify if the server is doing fine.