Solved create editable directory for wordpress access for plugin
The directory should exist but is currently owned by root, which is probably what causes the issue. Can you open a terminal into the app from the Cloudron dashboard and run
chown www-data:www-data /tmpthen try again?
If that works we can adjust the package to do so. Please note that the above command is not persistent!
Probably better to use a subdirectory under /tmp and not /tmp itself.