Custom Apache log format not being analyzed

We use the mod_log_config module in Apache with a custom log format:

"%{%Y-%m-%d %H:%M:%S}t %a %{SRC-Session}o %{SRC-Username}o %m %U \"%q\" %s %O %D %H \"%{User-Agent}i\" \"%{Set-Cookie}o\" \"%{Referer}i\" %p" src

In my profile, I have Log format: Apache, Custom, and entered the format string above. When processing I receive: "The analyzed log files don't contain any information, which can be analyzed by the program."

Can someone tell me what I'm missing?

Thank you in advance,

Michael