** Using WeBWorK **

When I choose the images display option, which I understand as generation of images via dvipng, I get the pink screen of which I am warned in the installation. I have tried the solution proposed in the installation directions, running
fmtutil --missing
but this does not help. The permissions seem to be correct since the timestamp on the tmp directory (/opt/webwork/webwork2/tmp) is being updated.

Can I debug the process in some way, say, by running the script by hand? Just for completeness, the error(warning) message I get is

cd /opt/webwork/webwork2/tmp/ImageGenerator.h7a4x67o && /usr/bin/latex equation > latex.out 2> latex.err failed to generate a DVI file at /opt/webwork/pg/lib/WeBWorK/PG/ImageGenerator.pm line 358.
cd /opt/webwork/webwork2/tmp/ImageGenerator.h7a4x67o && /usr/bin/dvipng -bgtransparent -D120 -q -depth equation > dvipng.out 2> dvipng.err returned non-zero status 256: No such file or directory at /opt/webwork/pg/lib/WeBWorK/PG/ImageGenerator.pm line 364.