Robson beat world number 117 Klara Koukalova in the first round but fell 6-2 6-2 to Oceane Dodin, ranked 151.
Robson, 22, returned from 17 months out in June but had a relapse and did not play until Indian Wells last month.
The former British number one has slipped to 465 in the world.
She will use her protected ranking of 58 to gain direct entry into the French Open main draw in May.
British number one Johanna Konta, the world number 22, is in the main draw in Stuttgart and will play Anna-Lena Friedsam in the first round.
Laura Robson failed to build on her best win since wrist surgery two years ago as she lost in the second round of qualifying for the WTA clay court event in Stuttgart.