UPS Plus is a new generation of UPS power management module. It is an improved version of the original UPS prototype. It has been fixed the bug that UPS could not charge and automatically power off during work time. It can not only perform good battery power management, but also provide stable voltage output and RTC functions. At the same time,it support for FCP, AFC, SFCP fast charge protocol, support BC1.2 charging protocol, support battery terminal current/voltage monitoring and support two-way monitoring of charge and discharge. It can provide programmable PVD function. Power Voltage Detector (PVD) can be used to detect if batteries voltage is below or above configured voltage. Once this function has been enabled, it will monitoring your batteries voltage, and you can control whether or not shut down Raspberry Pi via simple bash script or python script. This function will protect your batteries from damage caused by excessive discharge. It can provide Adjustable data sampling Rate. This function allows you to adjust the data sampling rate so that you can get more detailed battery information and also it will consume some power. The data sampling information can communicate with the upper computer device through the I2C protocol. UPS Plus supports the OTA firmware upgrade function. Once there is a new firmware update, it is very convenient for you to upgrade firmware for UPS Plus. The firmware upgrade can be completed only by connecting to the Internet,and execute a python script. Support battery temperature monitoring and power-down memory function. UPS Plus can be set to automatically start the Raspberry Pi after the external power comes on. The programmable shutdown and forced restart function will provide you with a remote power-off restart management method. That means you don’t need to go Unplug the power cable or press the power button to cut off the power again. You can set the program to disconnect the power supply after a few seconds after the Raspberry Pi is shut down properly. And you can also reconnect the power supply after a forced power failure to achieve a remote power-off and restart operation. Once it was setting up, you don't need to press power button to boot up your device which is very suitable for smart home application scenarios.
I was working on mounting a USB drive and needed to reboot the unit.... now the unit will not respond and the function button does nothing. What can be done?
Not normal at all. When I reboot the Pi on my UPS plus, it reboots without problems. No button needed.
Maybe you shut the Pi down and have some odd settings in your UPS plus?
The ultimate way to get out of such a situation is to take the batteries out and put them back in (without messing up polarity). And then study how you need to set up and operate your UPS. It is not necessarily obvious or easy to understand and do.
You can also do a factory reset (register 0x1B per the documentation). The documentation is also not very easy to grasp.
Or ... the UPS board could be defective, of course .... It happens, too.
ArjenR49
commented
3 years ago 
nickfox-taterli
I was working on mounting a USB drive and needed to reboot the unit.... now the unit will not respond and the function button does nothing. What can be done?