Google in its blog has recently announced that it is shutting down the legacy versions of many of its G Suite or Drive (Android and iOS) apps. Therefore, older versions of Google Docs, Google Drive, Google Sheets, and Google Slides will no longer work on smartphones as they will be shut down starting April 3.
The list of older app versions getting closed on April 3 is given below:
Google Drive for Android (prior to version 2.4.311)
Google Docs for Android (prior to version 1.6.292)
Google Sheets for Android (prior to version 1.6.292)
Google Slides for Android (prior to version 1.6.292)
Google Drive for iOS (prior to version 4.16)
Google Docs for iOS (prior to version 1.2016.12204)
Google Sheets for iOS (prior to version 1.2016.12208)
Google Slides for iOS (prior to version 1.2016.12203)
Google has further stated that users of these legacy versions will begin seeing prompts or pop-up messages to upgrade. The blog further mentions that after March 1, "some users with very old versions will be forced to upgrade when they receive the prompt."
So, if you are using any of these unsupported versions, you should download and install the latest version of that mobile application. However, Google has said that corresponding Web and desktop applications will not be affected by this change.
If you want to check what version your smartphone has, you can easily find the app's version type in the settings menu.