Old production version of screenly OSE is not really supported anymore for many reasons so I dont think you will get a lot of troubleshooting help for this scenario.
What I can advise on is that next time, you should create a wpa_supplicant.conf file ready with the wireless info for the place they are being deployed at and copy this file to the Pi’s SD card’s /boot/ directory, this will automatically load up on boot of the Pi and join the wifi you have specified on the file.
This is the tool I use to generate the wpa_supplicant.conf files: Wireshark · WPA PSK Generator
Enter the password for the wifi, and enter the SSID, then click Generate PSK.
When you get the result of that, create the file as I mentioned and enter the information on it as seen on this example:
If you entered all the information correctly and copy the file into the SD card /boot/ folder of the Pi, this should automatically join the Pi to the specified wifi upon boot.