My development license happened to expire and I was able to get an updated file from support. I followed the instructions Importing a license / Adding new servers in order to update my environment with the new license but it didn't seem to take. The license updated fine in Central Admin, but my site still had the red message that the license was expired. After a long time spent to make sure everything was in place and correct, the resolution came down to an IIS Reset. Immediately after this, all sites were up and running as expected.