In order to fix the issue, press Windows + Pause/Break key combination and open Device Manager. Look for the EP1032r-t's driver, right-click on its icon and press Uninstall. Reboot the PC and download and install the latest drivers available from the developer's page (Downloads). Also, update the Signage Manager Express software to the latest version using the update file from the Downloads section.
In order to upload the data to two different EP1032r-t devices, I recommend you connect them one by one to your computer, because there is no option to connect them both at the same time. The software allows you to use only one device at the same time:
Once you upload the data to the first device, disconnect it, restart the software, connect the second device and transfer the data. Also, since there isn't a user manual available, I suggest you contact the developers and ask for additional instructions if you need.