To update firmware in Printo H3+ printers via WiFi follow the instructions below.
Before moving to the next part, set USB port on the left side of Octoprint panel by selecting the port as illustrated.
In the Octoprint panel, on the right-upper side click on the key icon to open settings.
On the left side pick: Firmware Update.
To install firmware correctly, check if your settings are consistent with the illustration.
Click Flash firmware and wait until the uploading process comes to an end. During the update printer will stop working until the process is finished.