Re-direct loop

All I’m need to do is change wp-login to /login but when I enter this in the permalink settings I can’t access the login page from another browser:

Firefox has detected that the server is redirecting the request for this address in a way that will never complete.

Maxthon fails to load the page, as does IE.

Can you advise? There seems little scope to configure this incorrectly.

https://ww.wp.xz.cn/plugins/custom-login-url/