Ref. No. 1384/42-798
In the name of Allah the most Gracious the most Merciful
The answer to your question is as follows:
Labeling a product with Halal or Haram depends on its elements. We cannot say anything about protein powder before correct knowledge of its ingredients. You may seek guidance from the institutions that issue halal certificates for the same.
And Allah knows best
Darul Uloom Waqf Deoband