Weil's Tamagawa number conjecture for simply connected groups

Let $G$ be the generic fibre of a semisimple group scheme over a smooth projective curve over a finite field, and let $\tau(G)$ denote its Tamagawa number. A group is simply connected when its fundamental group scheme is trivial.

Weil's conjecture. If $G$ is simply connected, then

$$\tau(G)=1.$$

This is the Tamagawa-number assertion used in the paper to relate the Tamagawa number of a semisimple group to those of associated tori. The source does not state whether the conjecture is resolved.