When adding a new device via the web UI and setting the Wi-Fi credentials, certain valid SSID or password characters like ‘+’ are not properly encoded. Currently, ‘+’ is treated as a space, which is what ends up being added to the final balena-wifi-01 configuration.
Thanks for letting us know, I will ask our UI team to look into that. In the meantime you should be able to mount the boot media (SD card, USB stick, etc…) and edit the password manually in the /system-connections folder connection file. (It sounds like you already have done that, but adding the info here for others that may come across this…) See: Network Setup on balenaOS | balena