Comment 0 for bug 1871488

gnome-online-accounts does not synchronise accounts into the evolution data server. Therefore, calendars are not displayed in the gnome-calendar application or the time/calendar of gnome shell (when the clock in the centre of the top bar is clicked)

Manually adding all CalDAV calendars in Evolution resolves the issue, which makes me think the issue lies between gnome-online-accounts and the evolution data server.

This may be related to bug #1866999

ProblemType: Bug
DistroRelease: Ubuntu 20.04
Package: gnome-online-accounts 3.36.0-1ubuntu1
ProcVersionSignature: Ubuntu 5.4.0-21.25-generic 5.4.27
Uname: Linux 5.4.0-21-generic x86_64
NonfreeKernelModules: zfs zunicode zavl icp zcommon znvpair
ApportVersion: 2.20.11-0ubuntu24
Architecture: amd64
CurrentDesktop: GNOME
Date: Tue Apr 7 22:48:37 2020
InstallationDate: Installed on 2020-03-17 (21 days ago)
InstallationMedia: Ubuntu 20.04 LTS "Focal Fossa" - Alpha amd64 (20200315)
SourcePackage: gnome-online-accounts
UpgradeStatus: No upgrade log present (probably fresh install)