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Welcome. My name is ***** ***** would be glad to assist.
Based on your information, you have a loose neutral on the connection.
Go back to the point where you connected the new cable for the floor receptacle and check the white wire connection.
Make sure you have a good copper to copper contact on the wires, twist them a little around each other, then apply the wire nut.
Even though the other receptacle works, the loose connection is on the outgoing to the floor receptacle
That should get it cleared up.
Let me know what you find.