I'm seeing the same issue. Did you ever resolve this?
I had the exact same issue also. I had to grant the SQL access account sysadmin during the install instead of the dbcreator as stated in the documentation. After the install ran successfully, I removed the sysadmin permissions.
I can confirm that this worked. Took me hours to figure out that the DB user needs to have the "sysadmin" role in SQL for clean installs and version upgrades.
NOTE: The sysadmin Server Roles permission is an added requirement for fresh installs or upgrades to ePO 5.9. This requirement results from a defect corrected in ePO 5.9.1. The Sysadmin permission requirement was not by design.