Picking the wrong region looks like an authentication error
Temu routes API requests to different servers by region, and Türkiye falls under "Other Regions" in that split — meaning the Global region. When the wrong region is selected the error that comes back is a signature or authorisation failure, which pushes people straight to checking their keys. If your keys are correct and you keep getting authorisation errors, the region field is the first place to look.
There is a second region field: a numeric region code. It is used in the order listing filter and in the carrier list, and should not be confused with the first one. One decides which server you connect to; the other decides whose data you ask for.