issues getting Apple Music working on all devices

Hi. Hope someone can help.

I have setup the three month free trial of Apple Music, and whilst it works fine on my Mac, my iPhone and iPad don't seem to be able to access it.

Have been going around in circles for ages and looking online for solutions, but I'm not getting anywhere. Following the advice I've got online, I ended up changing my Apple ID password and, whilst this doesn't seem to be causing an obvious issue (I'm logged into all the devices with the new ID), I'm still unable to access Apple music on the iPad and iPhone.

The iPhone asks me to try it when I click on 'for you' but then tells me I'm already subscribed.

The iPad won't accept the new password and tells me that its is 'locked for security reasons'. I've followed the two step verification process steps here and ended up changing the password again, but it still gives me the locked message.

I'm sure there is is something I've done wrong, but this is getting so painful to solve.

Does anyone have any idea what steps I need to take to resolve this?

Thanks

Stuart