Water Table Rising - Is Sump Pump Working?

I had a new sump pump installed by my plumber about a month ago when the water table was very low. Since then, the table has risen to half the pit's depth, and the pump is completely submerged with no activity (I think... read on).
I'm now concerned that it is not working because I don't know if this new pump is very quiet when it operates. I can't tell from outside because where it drains is always soggy. I tried filling the pit with water when the table was low but the pit would not fill (not due to pump activity but I think because of water table).
The old pump we had a ball float that pumped the water when the float rose to a certain level. I don't see a float on the new pump, but it looks like there's a clear see through sensor the size of a dime on the top of the unit.
Can you tell me how I can test this, and how a submersible pump operates? Is it possible that the pump could be fully submerged but not operate until a higher level? How does one set the level for pumping?
My plumber is nowhere to be found :(
I have yet to see it working. The replacement
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Get out the hose and start running it into the sump. It should start before it fills. Also make sure the line to the pump is hot, maybe someone forgot to turn the breaker back on when they were done.
The pump likely works be a pressure switch and it is just not deep enough yet to kick on the switch.
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Joseph E. Meehan

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