  Since the launch of the Kepler space telescope in 2009 and the subsequent K2
mission, hundreds of multi-planet systems have been discovered. The study of
such systems, both as individual systems and as a population, leads to a better
understanding of planetary formation and evolution. Kepler-80, a K-dwarf
hosting six super-Earths, was the first system known to have four planets in a
chain of resonances, a repeated geometric configuration. Transiting planets in
resonant chains can enable us to estimate not only the planets' orbits and
sizes but also their masses. Since the original resonance analysis and TTV
fitting of Kepler-80, a new planet has been discovered whose signal likely
altered the measured masses of the other planets. Here, we determine masses and
orbits for all six planets hosted by Kepler-80 by direct forward photodynamical
modeling of the lightcurve of this system. We then explore the resonant
behaviour of the system. We find that the four middle planets are in a resonant
chain, but that the outermost planet only dynamically interacts in $\sim14$\%
of our solutions. We also find that the system and its dynamic behaviour are
consistent with \emph{in situ} formation and compare our results to two other
resonant chain systems, Kepler-60 and TRAPPIST-1.
