03-03-2017 Last Thursday 02-23-2017 a Google-wide security update was released and pushed out to disable the old level 1 SHA-1 128bit security encryption vehicle, being now replaced and upgraded on all Google users to SHA-2 256bit encryption requiring a re-login for all users. It is possible that something on your side is out of sync with Google - this may possibly be relieved by re-installing your Google Drive Sync app on the effected machines, or possibly updting your Google Chrome browser will achieve the same result if the backend Glip connector is via one of the Google extensions. Those of you who use Google integration tools may benefit from subscribing to the Google Blog.
I agree with Cecile that somehow you might be out of sync with your Google account. Can you access Google Drive "normally" without trying to access it via Glip?
I experienced the security update and I am able to access Google rive with no issues via Glip. Have you (and your teams) logged out of Google completely and then re-logged in?
Also, and it may seem mundane but it is a cure for many ills, have you and your team members rebooted your computers? I have several clients who fail to reboot for three months or more and wonder why things don't seem to work correctly. Just a shot in the dark.