Hi,
We have found one 100% repro step for this issue. An empty hosts file is the cause. We have a fix in the way. But in the meantime, can you check the content of your hosts file. It should be located here:
On Windows:
C:\Windows\System32\drivers\etc\hosts
On macOS:
/etc/hosts
Make sure the localhost host name is defined like this
127.0.0.1 localhost
Another solution other users have reported to work is to set the UNITY_NOPROXY environment variable to localhost:
On Windows command prompt,
setx UNITY_NOPROXY localhost,127.0.0.1
On Mac > terminal,
export UNITY_NOPROXY=localhost,127.0.0.1
If this fix does not work or if your hosts file is already correct, we also found out that anti-virus softwares can prevent the Unity Package Manager process to start. In that scenario, you can disable your anti-virus software for a few minutes to test if it works. If it did, configure your anti-virus to whitelist the NodeJS bundled with Unity (Under Unity installation folder, /Tools/nodejs/node.exe on Windows of /Tools/nodejs/bin/node on other platforms).
Let me know if it resolve the issue!
Pascal