Had a problem with mine 2 days after we brought our newborn home in the cold snap orange lamp on the control box lept coming on after the boiler had cut out when it was suppposed to fire - turned out to be the photo cell that senses the flame was just dirty and needed cleaning - took just 10 seconds to fix.
Which reminds me it is due a service - costs me about �35
Filling the tank could have disturbed sediment at the bottom of the tank and has now entered fuel line. Check for filters. We always switch off at tank when we have oil delivered and leave to settle for a couple of hours as recommended by our fuel supplier.
if you have an oil burner a red (in most boilers,some are green) reset button should be at the front of the boiler,turn on at power point/timer in the house and go to the boiler and press the reset button this should fire it up ok other than that the oil may not be getting through if you were running the tank on empty and may have blocked the filter with the bits that lie at the bottom of the tank this may need replacing,a handyman could do this very easliy.