Question: Error, `,` unexpected when using fsolve

Geometry := 2;
if Geometry = 1 then
    f_obj := 4.5;
    f_fluo := 125;
    f_TIE := 45;
    d_sample := f_obj;
    d_max := 250;
    d_cam := f_TIE;
    d_interlens := d_max - d_cam;
end if;
if Geometry = 2 then
    f_obj := 4.5;
    f_fluo := 125;
    f_TIE := 45;
    d_sample := 4.6;
    d_max := 250;
    d_interlens := d_max - d_cam;
end if;
                               2

                              4.5

                              125

                               45

                              4.6

                              250

                          250 - d_cam

TIE := (((((Distance(d_cam)) . (Lens(f_TIE))) . (Distance(d_interlens))) . (Lens(f_obj))) . (Distance(d_sample))) . (Vector(2, [distance, angle]));
           Vector[column](%id = 18446746239510517390)

d_cam_solved := fsolve(coeff(TIE[1], angle, 1), d_cam, d_cam = 20 .. 100);
Error, `,` unexpected

Hello, if I set d_sample to 4.6 then I get "Error, ',' unexpected when I try to find a solution using fsolve. However if I set it to 4.5 then the fsolve computes no problem and I get a solution. Does somebody know if this means fsolve has no solution or have I made a mistake somewhere else? Thanks