Can you check that its up to date, don’t just assume it is, you have to do it manually.
Go to the artifacts page (https://runtime.fivem.net/artifacts/fivem/build_server_windows/master/)
click the latest version - at the moment its
731-da11e5d04bcb33e534ac9be999238fa62bcedf83/ 21-Aug-2018 17:48 -
Click on it then download the server.zip. Drag everything in that zip file into your server’s folder, click replace for everything then restart your server.