I own a server and put my username on the "ops" file but when i log on it dissapears and i am not an op

Put the summary of the bug you're having here
I could not become an op on my minecraft multiplayer server
What I expected to happen was...:
Describe what you thought should happen here
I thought i should be an op
What actually happened was...:
Describe what happened here
My username got deleted from the ops file
Steps to Reproduce:
1. Put your username in the ops file and save it
2. start server
3. log on to server
4. look at the ops file again