WD My Book Studio II 2TB

Hi Everyone

I have an ancient WD MB studio II with 2 1TB HDD synced as one(don’t know the name)
i don’t use one of the drivers as backup so al in al I used all 2 TB for storage.

now I got an different HDD that I wanted do se whats on it, so I replaced one of the 1TB drivers in MB with the new one and booted it up,

and as it is obvious to me now it didn’t boot upp, so I replaced back with the original 1TB
and nothing happened, the External drives start lighting up and starts flashing.

so my guess is that because I started the unit with one of the HDD still in the case, the two HDD working as one bigger HDD now got out of sync and can’t mount. it isn’t even searchable in Disk Utility on my Mac book

is there a chance I can save the data on the HDD’s?