Charger not Charging :(

[maxters]

2013 Rockwood Premier Popup 1904
Same as Flagstaff/Mac 620ST and 206ST

So got the trailer back from the shop a few months ago (had to get the winch repaired)
I let the battery die, so ended up having to buy a new battery today.

Long story short, put the new battery in and connected the trailer to shore power and it's not charging (shows 12.something Volts) .

Where should I start troubleshooting?

I'm assuming that I may have to pop it up and look at the fuses on the WFCO Power center? Or is there something else that I'm missing?

It's in a small garage so I'm hoping I don't have to pop it up..
Any help or stories / suggestions / etc appreciated..