Yeah, you have to beat the first boss to access. Have you tried teleporting to another stargazer (bonfire of this game)?
I have beaten the 4th boss. And I'm starting to think that the weapon crafting isn't all that cracked up to be. First off, there can be a terrible damage debuff if you combine incompatible parts. Secondly, some weapon creations do not feel right. But the unmodded weapon designs do look amazing.
They also felt the need to add a fucking platforming section, AND enemies with projectiles that can knock you off. It's like sen's fortress, only there;s way less room to maneuver around.
As for parry system, apparently you have to hold down the block button a bit longer to get the effective stagger break