Unable to create new library after downgrading from 7.0.4 to 6.2.5

I’ve downgraded to 6.2.5 because I was unable to run Seafile 7.0.4, then everything seems back to normal, except I can’t create any library.

Here’s seahub.log entry

2019-08-11 15:45:11,671 [ERROR] seahub.api2.views:736 post Failed to add branch

My server runs on Ubuntu 16.04.6 LTS