The sequence 12-13-1 is invalid in 101 Okey because the ace is low only and cannot wrap around above the 13.

A run must be consecutive, and since the 1 sits below the 2, it can only appear at the bottom of a sequence, as in 1-2-3. There is no tile above 13, so the numbers do not loop. This rule differs from some Okey variants, so it is a common trap for newcomers. Plan your runs with the 1 only at the low end to stay legal.