I used the app for a couple of years when I worked for a company that didn't care whether I was nearly dead from fatigue or not. It's pretty useful and interesting if you can load your roster into it.
I found that the best and most reliable method of getting my flights in was from Roster Buster (which requires a subscription). There were occasional issues but I found that the Crew Alert support people were pretty good at sorting them out. Have you tried emailing them for a solution?
To be perfectly honest, now that I am no longer on Roster Buster, I have pretty much given up using Crew Alert as it has taught me what I need to know about how my body sleeps. The most useful aspect of it is that it very accurately predicted when I was unlikely to be able to sleep before a trip - so instead of lying in bed becoming frustrated I didn't even bother trying.