Nextcloud 12 Beta 2 upgrade to RC3

I have two hosted nextclouds.
Both at the same host.

Because I had some problems with the version 11.0.3, I have an update on version 12 beta 2 done with both clouds via the beta channel.
This worked with both Clouds also without problems.

Now my little problem.

I can do with one cloud no UpDate on RC3.
The Updater opens. But when I press the startup update button nothing happens.

In the other cloud, the update to RC3 worked fine.

Where do I make the mistake?

I would be very thankful for help.
With the support of my host they told me that there is no support for beta versions.

Excuse my bad English.

That’s a known issue and it has been fixed in beta 3. As far as I know the only thing you may do is to run the update from command line.

Go to your NC document root and run this command:
sudo -u www-data php updater/updater.phar

Note: ‘www-data’ is the name of the owner of your webserver processes. It may be different on your system.