Neptune Systems insists that you use a hardwired (ethernet cable) connection when performing firmware updates. Its step 1 and 2 if you read the instructions.
"To update the firmware follow the following procedure:
First, confirm Apex is directly connected to your to your home Wi-Fi router.
Please do not do firmware updates over Wi-Fi
If connecting to Apex to your home router is not possible, see here
Second, connect the computer you downloaded the firmware on too with your Wi-Fi router via an Ethernet cable. Disable the wireless on that computer."
https://www.neptunesystems.com/firmware/