Anti-Virus Schedule not working

I recently installed Comodo Anti-virus and have been very pleased. Intsall went without a hitch. Problem I have now is the Scheduler. I set up a schedule to test it- the program did a scan on a Thursday. Now the schedule will not work. I can set up a daily scan at 1am and it will not run. Is there something else I need to do? Manual scan will work fine. Thanks. Pat