[OJS 3.1.2.1] Unable to install (or upgrade) plugin via plugin gallery

I just installed the latest version of ojs, OJS 3.1.2.1
I tried to install the plugin for my new OJS through the plugin gallery. but when I click install and then a pop up appears as shown below, and then i click “ok”, but the “ok” button doesn’t process anything. please help me.
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Hi @Misbakhul_Akbar,

Check your PHP error log for details.

Regards,
Alec Smecher
Public Knowledge Project Team