If you already started receiving messages on your brand-new Android device and want to merge them with the old iPhone messages, you need to proceed like this.
Please note that recent Android WhatsApp versions use a particular archive format (msgstore.db.crypt8-9-10) that's not automatically decryptable by WazzapMigrator. This is due to WhatsApp recently changing its encryption so that a particular elevated access (root) is required. Absolutely no app can automatically extract the decryption key, as it's specific to your own device and requires the device to be connected to your PC/Mac. Please refer to crypt8 page to know how to decrypt it manually, or just do NOT tick "Merge Android archive" in WazzapMigrator.