No point in guessing, start at square one and proceed in an orderly fashion..
If- the tank has water in it, then the water that escaped has been replaced with air. If -- the leak in the pipe only opens under pressure then the tank wont lose water whilst the engine is not running..
I think you need to follow the procedure for refilling your engine with coolant..
Then check for leaks, if the leak is bad enough to make a puddle under the car it should be easy to find..
For the moment, as there if no proof it's correct, ignore the "no circulation" bit untill it can either be verified or disproved..
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