Unplug the sump pump first and first and foremost. Examine your discharge pipe to ensure it is clear of debris and the ice. Remove any obstructions. To make ice, you could require a heater as well as a hair dryer.
When you are inside then loosen the clamps on the hose to allow you to remove the boot made of rubber. The cover needs to be removed and the pump lifted off of the pit. After checking to see whether the intake filter is free of dirt or not remove the discharge hose in order to determine if there is a blockage.
Make sure to clean the pit thoroughly to eliminate all obstructions that could block the pit. Test this pump simply by plugging it in, and using to turn on flow.
After that, you can place the sump pump into the pit. Ensure that there is no obstruction to the flow switch. Reassemble the pump then run a dry test.