Should’ve kept v3.0.0 in beta 
I wish Unity would stop rushing releases; this has been a norm for years I hope to see break one day.
Repro’d every time.
Experiencing same thing.
I somehow downloaded unity editor after, but I couldn’t even open the project with it through the hub.
The editor sets to default for installing versions a non-existing disk, I changed it and it works perfectly now
Bunun neden olduğunu anlamıyorum
I had this same problem today, where the Hub showed “Available: 0 bytes” and wouldn’t allow any installs. In my case, the cause turned out to be Windows Defender–it apparently wasn’t allowing Unity Hub access the disk, so the Hub was somehow receiving or defaulting to a value of 0 bytes. Normally when an app attempts to install something or change system settings, Windows Defender will put up a full screen prompt requiring you to confirm before proceeding. For some reason this wasn’t happening when installing Unity vis the Hub.
The only way I could get it working was to try changing the install location (gear → Preferences → Installs → Installs Location). Once I tried to save a new installs location, only then did Windows Defender come up with the full-screen prompt. After I clicked “yes”, the Hub’s install "Available: " display showed the actual free bytes (like 80GB), and I was able to install Unity editor after that.
I Changed the disk to the newest 3.4.1 but it says only 46.23 MB of space 
I figured out how to fix it on my mac! On Unity hub, I clicked the gear and then changed install location to documents. Now I have 730.62 GB of space! Try it!
Hey that’s work thank you
