Are you including the file extension in the config option? (Extension type doesn't matter but it must be included.)
pen_table_file H:\Library\Plot\pen_table.txt
Here's my pen table file. Looks like maybe you need semicolons and the word "color" in your file.
! This Pen Table will print everything in black and white except
! user defined colors.
pen 1 thickness .003 in;
pen 2 thickness .003 in; color 0 0 0;
pen 3 thickness .003 in; color 0.2 0.2 0.2;
pen 4 thickness .012 in; color 0 0 0;
pen 5 thickness .006 in; color 0 0 0; drawing_color;
pen 6 thickness .003 in; color 0 0 0; quilt_color; magenta_color; attention_color; curve_color;
pen 7 thickness .003 in; color 0 0 0; datum_color;
pen 8 thickness .003 in; color 0 0 0; dimmed_color; section_color;