: Devices running Android 2.3.7 and older can no longer create new accounts or re-verify existing ones. Minimum Requirements : Currently, WhatsApp requires Android OS 5.0 or newer

Since the Play Store won't help, you need to allow installations from other sources.

WhatsApp has effectively bricked its service on Gingerbread, and for good reason: keeping millions of devices on outdated, insecure software poses a risk to the entire network.