The problem may be with the Teac unit itself rather than the app. I have read that some people have had problems with them. Who did you buy it from, used or from a dealer?
You may be aware of this thread already, but if not, check it out:
https://forum.audiogon.com/discussions/teac-nt-505-impossible-connecting-to-wifi-router-o-such-lan-help-me-pl
You may be aware of this thread already, but if not, check it out:
https://forum.audiogon.com/discussions/teac-nt-505-impossible-connecting-to-wifi-router-o-such-lan-help-me-pl