No automatic update from Nextcloud 20.0.10 to nc21?

Sorry if this is a silly question but i did not find something about my problem at the forum.

I have NC 20.0.10 on an arm64 (RockPro64) running.
At settings i have ‘stable’ for the update channel.
On the forum i see that NC 21 is released but my system tell me that it is up-to-date.
What did i miss?

Many thanks for your help