If you use an HTTP(S) proxy server to access the Internet, make sure that WinHTTP settings are properly configured on Microsoft Windows machines with Veeam backup infrastructure components.
The following command will set the proxy (all protocols) to 192.168.111.111 port 8888:
netsh winhttp set proxy proxy-server="192.168.111.111:8888"
Current WinHTTP proxy settings:
Proxy Server(s) : 192.168.111.111:8888
Bypass List : (none)
It is important not to specify "https".
Known Limitation: WinHTTP does not support authentication.