CDR exports is not working any more

Hello all,
I have a problem with the CDR exports function. I do not know why, it stopped working. All I can see is that the file i.e. 26.csv.gz is created in /tmp but its size is 0kB and the status in the cdr exports page is “Pending”. Then, after a while it turns to the “Failed” status.
Please give me a clue where to look, to find out what is happening.
Thank you!!

There is not enough information to say anything. Could you provide at least logs with error?