I was testing out the Spring 2020 WVD recently and thought I would try the new 2004 Windows 10 version (primarily to test out MSIX App Attach) and come across a weird error.
It seems that if 2004 is deployed to Fall 2019 WVD it deploys without issue and can be connected via both the Web Client and Desktop Client.
If however you deploy it to Spring 2020 WVD you may be unable to connect.

It appears to be due to the failed install of the RDInfraSxSStack.
If you suffer this problem you will need to do the following:
Logon to the Session Host directly via RDP.
Open CMD Prompt (as Admin)
Change Directory to : C:\DeployAgent\RDInfraSxSStackInstall\
Then run:
MSIEXEC /i SxSStackInstaller-181129002.msi /l*v C:\sxs.log

This should reinstall RDInfraSxSStack and then you should be able to connect.

For reference the reinstall didn’t work for me via GUI. Not sure why but I got the following error:

Obviously I hope this is something Microsoft fix as not ideal if you’ve deployed 10+ session hosts!
James