Back Office Not Working

[dontbesorry80]

Hi,

I just tried installing this. I can see the new Tab but it doesn't let me save or add any new redirects. When I delete I get the following error in the console:
DELETE http://XXXXXX.com/umbraco/backoffice/Simple301/RedirectApi/Delete/undefined 400 (Bad Request)

I'm using Umbraco version 7.4.3