Unlock subscription button

Hello,

I have some trouble at managing podcasts in iTunes.

A couple of weeks ago I changed my laptop, installed last version of iTunes, and import my libraries and podcasts from the old laptop. Everything worked fine, except than subscriptions to podcasts: I've got them all in My podcasts list, but their status is "non subscribed". I select any of those "non suscribed", go to "Settings" and there is a subscription button in "off" position; I try to change it to "on" position, but there's a small lock on it and therefore is not possible to move it.

Why is this button locked? How can I unlock it?

iTunes 12.1.1.4

Windows 8.1

Thank you,

Nieves Navas