Logs not recording?

I have gotten my logs to record before, but rarely and I do not know why they are not always 100%. I have everything installed, I do /combatlog and it says it is recording. I kill a bunch on bosses, go to upload, and nothing is there. Only a few trash mobs from right as I first started recording. Other times it will work 100% fine. I have no idea why this happens, the files only get to be a few MB before they stop, while when they work, they get to be 100MB. Any solutions? Thanks.

Firstly, you can check if boss fights present in your log file. Just open your log file with any text editor (like notepad) and search for ENCOUNTER_ string.

Each boss fight should have following pair of events:

<time stamp> ENCOUNTER_START,xxx,<Boss Name>,xxx,xxx
... another events here...
<time stamp> ENCOUNTER_END,xxx,<Boss Name>,xxx,xxx,x

If there are no such pairs in your log file then something wrong with logging: system prevent from saving (large file size, not enough free disk space, …), something turns off logging (logout, disconnect, addons, …), bug in WoW client