The new Gmail app update is featured to include an offline mode in the app itself, which means that the previously used Gmail offline Chrome app that helped to enable functioning offline, will not be necessary anymore. Following the redundancy of an unnecessary app, Google announced to roll back the app, a legit decision by all means. The G Suite Updates Blog stated, "We’ve heard from customers that they want to use the same Gmail app whether they’re online or off. Our new offline feature makes that possible, allowing you to search, write, delete, and archive up to 90 days of messages, even when you don’t have an internet connection. This native capability is easier to use and performs better than the Gmail Offline Chrome App, so we’re removing it from the Chrome Web Store after December 3rd, 2018. This is a part of our ongoing effort to move Chrome apps to the web." If you are still using Gmail Chrome offline app, it's advised, from the ends of Google, to uninstall the app and move to the new built-in functionality of the new Gmail app. It's still a long time since the app is completely removed from the Chrome web store, which is supposed to be on and since 3rd December, it's suggested that you go and do it as soon as you can so as to be well versed with the new Gmail offline setup. In case you are a G Suite admin that wants to maintain this functionality for users, you are entitled to enable the option at a domain level and then instruct your users to do it the same way.