Upload problem in the web


I installed the owncloud in ubuntu system with the LAMP environment. Versions are belowed:
owncloud: 10.0.2
ubuntu: 14.04
Apache: 2.4.7
Mysql(Mariadb): 5.5.54
Php: 7.0.1

I have successfully log in the website and created a new dir and uploaded a new file. However, when I try to upload files in the other day. It said "Problem loading page, reloading in 5 seconds".

I try to restart the apache2 service already but the problem still remains. I also try to upload all size of files, none is successful.

Can anyone tell me how to fix the problem? Thank you.

Are you using a real server / computer or a docker container or a virtual machine?

also, what does the log say?