Error with form

Hello

I have a problem with the form in the right column here: http://www.folkets-stralevern.no. When you enter your email and click the SEND button, it shows the text:

Oops! There is a problem with this form:
textStatus:error
errorThrown:Not Found
responseText:

I updated the widget to a newly created form, but it also shows the error.

https://ww.wp.xz.cn/plugins/wysija-newsletters/