Hi,
ownCloud 8.0.4 is outdated (8.0.16 was the latest release of this branch so you’re missing 12 updates). Furthermore the 8.0.x branch is end-of-life and unsupported since the end of the last year.
Finally its strongly discouraged to run ownCloud on a QNAP device for the reason explained in [1] and [2]. QNAP is not capable to provide a recent version of a system library (libxml 2.7.0 released around 8 years ago) which is needed for running ownCloud.
You might want to contact the QNAP support about this issue. If more QNAP users are stepping up and nagging their support then they might change their minds and provide recent and up2date software versions.
[1]
[2]