Few weeks ago, I was still able to use EP for uploading csv files. But now, after waiting for around 30 seconds, it prompt me "page not found", that means no response. I've checked the tempEP folder, my uploading csv file is there, it just can't be read into the system.

After seeing this problem, I tried to upgrade to EPv1.2.5.6, but the problem persist.
[but after upgrade to v1.2.5.6, it still shows v1.2.5.5 in the EP panel. Is it normal?]

I am not sure what caused the problem. This is what I've done for the past few weeks, any expert got an idea?

1. My whole website is relocation to a new server.
2. Installed admin folder rename security patch