What could be causing my app google engine cron job not to work?

What could be causing my app google engine cron job not to work?

I've the following in cron.xml on my WEB-INF directory:
?xml version="1.0" encoding="UTF-8"?>
<cronentries>
<cron>
<url>/?brtyuioacdwer</url>
<description>Load datastore</description>
<schedule>every monday 06:17</schedule>
<timezone>America/New_York</timezone>
</cron>
</cronentries>
But when the time comes to execute the shown URL nothing seems to happen
as my datastore keeps the same, of course I've tested to call the URL from
browser and it does its work nicely and I've uploaded new version of the
app several minutes before it should be automatically executing. I don't
know if there might be some problems with cron jobs when they try to write
on datastore or if they are not the default version af the web
application, so I'm asking for some guide.
Thanks for your attention.