Im trying to update my NC to the lastest version , but it wont go beyond 25.0.10 , it can’t detect newer major versions , I’m using a Hansson IT appliance :
$ sudo -u www-data php --define apc.enable_cli=1 /var/www/nextcloud/updater/updater.phar
Nextcloud Updater - version: v25.0.3-2-gd49ee0d
Current version is 25.0.10.
No update available.
Nothing to do.
Have you tried briefly switching the update channel to beta?
After update you can switch back to stable.
Hope that helps,
much luck!
I did , but the result is the same 
Look at system requirements, then have a look at your PHP version: php -v.
Maybe that’s the reason?
https://docs.nextcloud.com/server/26/admin_manual/installation/system_requirements.html