I don't have the wtiu or tried the new download.
It just sounds like you're trying to update the app and not the WTIU. I'm probably way off here. I'm just guessing.
Where's the update button?
https://d2frr7198pxftr.cloudfr...12/DCS%20WTIU%20User's%20Guide.pdf?VersionId=YjXWFjc_0TL9r4VsiiGTS5mEWBribyYj&fbclid=IwZXh0bgNhZW0CMTAAAR0yGEG3a7jm7gJ3q6IS-m5VuvoSj27lo88moDw9BhplOR-_0q9hUPFTNxk_aem_zRM2oNqahBZ7FM0upzbdwA
see page 11
I'm using the directions provided with the WTIU Firmware update today. I put the WTIU in WTIU Wifi mode (not connected to my home wifi), connect directly to that with my device (I've tried multiple), then I open the LuCi interface and go through the steps for the firmware upgrade.
Interestingly, LuCi says my firmware version is updated to the correct version v1.2, but in the DCS app the WTIU firmware is still listed as the old version V1.06.