GFCI issue with grounded protected receptacle
The hot line side needs to have the black wire to the brass screw on the line connector side. The white wire from the same cable that the black came from goes to the silver line side.
The load side to your outlets black to brass and white to silver and the bare coppers tied together and attached to the GFCI and outlet ground screws usually green in color.
I believe you have swapped your White neutral from line to load and that will cause the problem you describe.