Lately I receive these errors. I am running Ubuntu 16.
W: An error occurred during the signature verification. The repository is not updated and the previous index files will be used. GPG error: http://apt.insynchq.com/ubuntu xenial InRelease: The following signatures were invalid: KEYEXPIRED 1473479811 KEYEXPIRED 1473479811 KEYEXPIRED 1473479811 KEYEXPIRED 1473479811 KEYEXPIRED 1473479811 KEYEXPIRED 1473479811 KEYEXPIRED 1473479811
W: Failed to fetch http://apt.insynchq.com/ubuntu/dists/xenial/InRelease The following signatures were invalid: KEYEXPIRED 1473479811 KEYEXPIRED 1473479811 KEYEXPIRED 1473479811 KEYEXPIRED 1473479811 KEYEXPIRED 1473479811 KEYEXPIRED 1473479811 KEYEXPIRED 1473479811