Software updates stuck at 0% Downloading

We have new SCCM environment 1910 version. Testing software updates on some test machines. On all Win 8.1 test machines, patches got installed. On all Win 10 machines updates are stuck at 0% downloading. All these Win 8.1 and Win 10 machines are in same subnet and checked for boundary and boundary groups. Please let me know what else i have to check or verify.