  There is currently a severe discrepancy between theoretical models of dust
formation in core-collapse supernovae (CCSNe), which predict $\gtrsim 0.01$
M$_\odot$ of ejecta dust forming within $\sim 1000$ days, and observations at
these epochs, which infer much lower masses. We demonstrate that, in the
optically thin case, these low dust masses are robust despite significant
observational and model uncertainties. For a sample of 11 well-observed CCSNe,
no plausible model reaches carbon dust masses above $10^{-4}$ M$_\odot$, or
silicate masses above $\sim 10^{-3}$ M$_\odot$. Optically thick models can
accommodate larger dust masses, but the dust must be clumped and have a low
($<0.1$) covering fraction to avoid conflict with data at optical wavelengths.
These values are insufficient to reproduce the observed infrared fluxes, and
the required covering fraction varies not only between SNe but between epochs
for the same object. The difficulty in reconciling large dust masses with
early-time observations of CCSNe, combined with well-established detections of
comparably large dust masses in supernova remnants, suggests that a mechanism
for late-time dust formation is necessary.
