Decompiled result looks liks this

__int64 __fastcall main_main(__int64 a1, __int64 a2, __int64 a3, __int64 a4, __int64 a5, __int64 a6)
{
  __int64 v6; // r8
  __int64 v7; // r9
  unsigned __int64 v8; // rdx
  unsigned __int64 v9; // rcx
  unsigned __int64 v10; // r8
  __int64 v11; // rdx
  __int64 v12; // r8
  __int64 v13; // r9
  __int64 *v14; // rcx
  __int64 i; // rdx
  int v16; // er8
  int v17; // er9
  __int64 v18; // rdx
  __int64 v19; // rdx
  __int64 result; // rax
  __int64 v21; // r8
  __int64 v22; // r9
  int v23; // edx
  int v24; // ecx
  int v25; // er8
  int v26; // er9
  __int64 v27; // rdx
  __int64 v28; // rdx
  __int64 v29; // [rsp+8h] [rbp-100h]
  __int64 v30; // [rsp+38h] [rbp-D0h]
  unsigned __int64 v31; // [rsp+40h] [rbp-C8h]
  __int64 v32; // [rsp+48h] [rbp-C0h]
  __int64 v33; // [rsp+50h] [rbp-B8h]
  char v34; // [rsp+78h] [rbp-90h]
  char v35; // [rsp+80h] [rbp-88h]
  __int64 v36; // [rsp+98h] [rbp-70h]
  __int64 v37; // [rsp+A0h] [rbp-68h]
  __int64 *v38; // [rsp+A8h] [rbp-60h]
  __int128 v39; // [rsp+B0h] [rbp-58h]
  __int128 v40; // [rsp+C0h] [rbp-48h]
  __int128 v41; // [rsp+D0h] [rbp-38h]
  __int128 v42; // [rsp+E0h] [rbp-28h]
  __int128 v43; // [rsp+F0h] [rbp-18h]

  if ( (unsigned __int64)&v35 <= *(_QWORD *)(__readfsqword(0xFFFFFFF8) + 16) )
    runtime_morestack_noctxt();
  *(_QWORD *)&v42 = &unk_4C6B00;
  *((_QWORD *)&v42 + 1) = &off_50BB80;
  fmt_Fprintln(
    a1,
    a2,
    (__int64)&go_itab__os_File_io_Writer,
    (__int64)&v42,
    a5,
    a6,
    (__int64)&go_itab__os_File_io_Writer,
    os_Stdout);
  *(_QWORD *)&v41 = &unk_4C6B00;
  *((_QWORD *)&v41 + 1) = &off_50BB90;
  fmt_Fprintln(
    a1,
    a2,
    (__int64)&go_itab__os_File_io_Writer,
    (__int64)&v41,
    v6,
    v7,
    (__int64)&go_itab__os_File_io_Writer,
    os_Stdout);
  time_Sleep(a1);
  main_getMacAddr(a1, __PAIR128__(v8, a2), __PAIR128__(v10, v9));
  v32 = v29;
  v37 = 1000000000LL;
  *(_QWORD *)&v43 = MEMORY[9];
  *((_QWORD *)&v43 + 1) = 1LL;
  log_Fatal(a1, a2, 1000000000LL);
  if ( v29 <= 0 )
  {
    result = 0LL;
  }
  else
  {
    v14 = (__int64 *)v37;
    for ( i = 0LL; ; i = v33 + 1 )
    {
      v38 = v14;
      v33 = i;
      strings_Replace(a1, a2, i, (__int64)v14, v12, v13, *v14, v14[1], (__int64)&unk_4F040B);
      if ( v31 < 6 )
        runtime_panicSliceAlen(a1, a2);
      v36 = v30;
      runtime_concatstring2(a1, a2, v31, (unsigned __int64)&v34, v16, v17);
      strings_ToUpper(a1, a2, v18, 0LL >> 63);
      main_GetSHA256Hash(a1, a2, v19, 6LL);
      if ( v30 == 64 )
        break;
      if ( v33 + 1 >= v32 )
      {
        result = 0LL;
        goto LABEL_9;
      }
      v14 = v38 + 2;
    }
    runtime_memequal(a1, a2, v11, (unsigned __int64)&unk_4F827F);
    *(_QWORD *)&v40 = &unk_4C6B00;
    *((_QWORD *)&v40 + 1) = &off_50BBA0;
    fmt_Fprintln(
      a1,
      a2,
      (__int64)&go_itab__os_File_io_Writer,
      (__int64)&v40,
      v21,
      v22,
      (__int64)&go_itab__os_File_io_Writer,
      os_Stdout);
    time_Sleep(a1);
    runtime_concatstring2(a1, a2, v23, v24, v25, v26);
    strings_ToUpper(a1, a2, v27, 6LL);
    main_GetMD5Hash(a1, a2, v28, 6LL);
    main_AESDecrypt(a1, a2);
    result = 1LL;
  }
LABEL_9:
  if ( !result )
  {
    *(_QWORD *)&v39 = &unk_4C6B00;
    *((_QWORD *)&v39 + 1) = &off_50BBB0;
    result = fmt_Fprintln(
               a1,
               a2,
               v11,
               (__int64)&go_itab__os_File_io_Writer,
               v12,
               v13,
               (__int64)&go_itab__os_File_io_Writer,
               os_Stdout);
  }
  return result;
}

As we can see, the program takes the HMAC of our computer, replaces : with nothing, slice the string to take the first 6 characters and then appends the 6 characters to the original string
and that result is upper cased and then sha256ed and then compared with a sha256 from the binary (a31ebf3ec8bd0d9b991a3291058e6e67323f06e4ea8903bcf7d1942ab71ac114), we need to bruteforce this using script
from hashlib import sha256

for i1 in range(256):
    print i1
    for i2 in range(256):
        for i3 in range(256):
            a = (('%x'%i1).zfill(2)+('%x'%i2).zfill(2)+('%x'%i3).zfill(2)).upper()
            a = a + a
            if 'a31ebf3ec8bd0d9b991a3291058e6e67323f06e4ea8903bcf7d1942ab71ac114' == sha256(a).hexdigest():
                print a

and we find F09FC2F09FC2 so our MAC must begin with f0:9f:f2, we spoof our MAC and then when we execute the program we get the flag

Ubiquiti™ SecuStore® v3.1.342
Checking local hardware fingerprint
Local hardware identity verified! Decrypting Secrets...
flag{M@C_!s_n3ver_a_g00d_HW!D!!}