Private servers like Turtle WoW, Elysium, and the now-defunct Nostalrius all built their cores around this version. Consequently, any modern WoW Classic emulation requires the build (the hexadecimal build number often listed as 1.12.1.5875 ).
The REPACK’s wow.exe is patched incorrectly, or your realmlist.wtf points to a server running a different patch. Fix: Download a fresh wow.exe from a trusted source like "Lumy’s Vanilla Repack." WoW Vanilla Client 1.12.1 Portable Free Download -REPACK
A "Portable Repack" differs from standard installers by being self-contained. [Client] Why 1.12.1? - OwnedCore Private servers like Turtle WoW, Elysium, and the