Using the Mog Station

[Niwashi]

But my question is, if I don't have a subscription yet, am I still able to use the Mog Station (Still using my free 30 days)?

That shouldn't matter. If you were on the Free Trial (i.e. had not purchased the game yet), then you'd be restricted from Mog Station purchases, but the 30 days you get with purchase of the game gives all the same privileges as a standard subscription.

I don't know what the problem is, though, only that that isn't it.