error message

It was working fine successfully.
started giving me error message. all it says is server error without any details.
when I check posts, I see that it uploaded 14 lines / posts successfully.
when I repeat, it will only upload 14 lines / posts while at the same time giving the same error message.
my file is small so it is not too big as I uploaded files of bigger size before.
Thanks for reading. hope you can direct me to the right place to fix this error.