I am trying to get a metapost drawing as logo added to right upper corner of a DIN B style letterhead, but it does not show up, just the letter itself. Is there anything to change to the layers for the MP toe reveal itself?

Thanks, Jeroen

% BEGIN MP LOGO SETUP

\startuseMPgraphic{mpglogo}
  path p;
  p := (0,0)--(100,0)--(100,100)--(0,100)--cycle;
 
  path q;
  q := p cornered 30pt;
  draw q withcolor black withpen pencircle scaled 7pt;
\stopuseMPgraphic

\definelayer
  [logo]
  [repeat=no]

\setlayer
  [logo]
  [hoffset=160mm,voffset=17mm]
  {\scale[width=25mm,height=25mm]{\useMPgraphic{mpglogo}}}
 
\setupbackgrounds[page][background=logo]

% END MP LOGO SETUP, BEGIN LETTER SETUP

\usemodule[letter][style=dinb]

\setupletterlayer
  [reference]
  [list={name,phone,email,date}]
 
\setupletterlayer
  [address]
  [y=55mm]
 
\setupletterdescription
  [enclosure]
  [location=top,
  leftmargin=0.5em,
  symbol=#1,]

\usesymbols[mvs]
\definesymbol[1][{\symbol[martinvogel 2][PointingHand]}]

\setupletter
  [toname={John Doe},
  toaddress={201, Main Street\\23124 London\\United Kingdom},
  fromname={Jansen NV},
  fromaddress={Waalhaven 2200\\2842 KL Rotterdam},
  name={Piet jansen},
  phone={+31(010)4234 4232},
  email={peter.jansen@gmail.com},
  date={\currentdate},
  signature={\externalfigure[autograph][height=4\lineheight]\\\correspondenceparameter{name}},]

% END LETTER SETUP, START LETTER
 
\startletter
  [subject={Outstanding Invoices},
  opening={Dear Sir,},
  closing={Kind Regards,},
  enclosure={list:Commercial Invoice,Accounts Statement},]

\dorecurse{3}{\input knuth \par}

\stopletter