You say you convert the text:
00020126580014br.gov.bcb.pix0136123e4567-e12b-12d1-a456-426655440000
5204000053039865802BR5913Fulano de Tal6008BRASILIA62070503***6304
and you get: 0x1D3D
using:
poly: 1021 and init: FFFF
But on this website we see that this text generates: 80BF