Installing MacOS on a older Mac

So I have an old MacBook Pro I got out of a storage unit. Model A1278

The Mac originally booted up to what I assumed was high sierra, I went to reset the Mac & am now having issues getting high sierra back on it. The installer in macOS recovery says that the online server can’t be reached. I attempted to run a usb installer for the Mac but I’m getting a screen with a flashing circle with a line through it, after some research I discovered this is because the version of macOS is not compatible with this Mac, however when I google the latest version of macOS I can run on this computer it says high sierra. Also since the computer wants to download high sierra VIA macOS recovery I’m guessing it is actually compatible with this computer. I also attempted to downgrade it to snow leopard via an official cd copy from Apple and got the same error, but with the Mac repeatedly beeping 3x in a row over and over.

Ive tried installing over WIFI & Ethernet, tried resetting the PRAM, tried adjusting date & time settings with terminal. I’ve tried just about every trick I can find online with no luck :(

long story short. What software do I need to put on this thing to make it work again?

after running the serial # through a checker this should be the exact model and specifications.