A Unity ID allows you to buy and/or subscribe to Unity products and services, shop in the Asset Store and participate
in the Unity community.
Here is what helped me. https://forum.unity.com/threads/package-manager-buggy-glitchy.1042618/
Hope this is also the case for you.
I can confirm that. Had similar issues for some weeks now. Then I saw this post today and remembered that some time ago I have upgraded my...