If you want to proceed for experimental or hobbyist purposes, you must find the exact archived version that used to support Gingerbread. The final builds supporting Android 2.3.6 are generally within the series or older. Step-by-Step Download Guide
Attempted Fix: Some users temporarily bypass this by rolling back their phone's system date to 2014 or 2015 in the settings. However, this will break internet connectivity for most web browsers and other apps. 2. "Temporary Ban" or "Update WhatsApp" Screen Download Whatsapp Old Version For Android 2-3-6