CT slice reconstruction using pytomography

Dear all,
i have been simulate the CT scan of chest using GATE, i stuck all my projection in a matrix creating a sinogram, i saved it in a dicom file, i tried to reconstruct the CT slice, following this example: DICOM-CT-PD (3rd Generation CT) — PyTomography 3.2.2 documentation
but it doesn t work, any help please
regards