Do not confuse it with the domestic Hepsiburada connection
HepsiGlobal is Hepsiburada's export channel and runs entirely separately from the domestic Hepsiburada connection: a different panel, different credentials, a different setup. The fact that your domestic connection works means nothing here. You take the keys from the integration section at seller.hepsiglobal.com.
Stock and price updates carry a company identifier. Although the field looks optional, it has to be filled in for updates to be written to the right account; it is visible in the Seller Portal.