NanoPi M3 does not boot after installation of OpenVPN

Fresh install of DietPi on a NanoPi M3. Updated the system, then rebooted. Installed openvpn. Rebooted.
M3 does not boot anymore.
Blue led blinks a couple of times then it turns off. Red led is on.

Have no idea what happened.

Today it booted again regularly.
Mysteries of the SBCs.