CANNOT PRIME PUMP AFTER DESCALING - therefore...

Question

Per descale instructions, I followed instructions and descaled with vinegar - then let sit for 4 hours. Upon start up - pump will not prime - I have verified more than ample water in the reservoir. I've tried unplugging and let it sit for an hour. I've ensured the "handle" is lowered tight down to make contact - can't find a sensor anywhere in that area although I have tried cleaning the area thoroughly to remove minor coffee grind residue (film).
Red light next to "Heating" remains ON at all times - cannot get pump to prime and consequently cannot get EITHER small or large cup blue lights to illuminate. Unit is 4 months old and has performed flawlessly for 10 cups daily since March. I descaled 2 months ago with vinegar and everything returned as normal. Not this time. Stuck! Any suggestion? Many thanks, Bruce