Use this as your guide to create your own OTA path:
Direct path to 2.15 OTA: https://raw.githubusercontent.com/InovelliUSA/Firmware/main/Blue-Series/Zigbee/VZM31-SN-2-1-Switch/Beta/2.15/VZM31-SN_2.15.ota
The Github: https://github.com/InovelliUSA/Firmware/tree/main/Blue-Series/Zigbee/VZM31-SN-2-1-Switch/Beta/2.15