Thanks for your response @Tambun_Sihotang. Without any error log messages it can be difficult to ascertain the issue. There are several posts where users have encountered this error and managed to resolve them - you may wish to have a look:
That said, this error is not necessarily related to the issues that others may have had with their OJS installs and may be unique to your OJS installation - typically error logs give a better indication of what the issue is, but in your case, it’s difficult to say. Another community member or PKP team member may be able to provide some help if they have an opportunity.
-Roger
PKP Team