Funding HSA for 2016

We spent our FSA funds by 11/30/16 and had HDHP insurance effective 12/1/16. The FSA plan for the company was not closed until 12/31/16 although our individual account was -0- @ 11/30. We opened an HSA bank account on 12/1. Can we contribute the full amount for 2016 in the amount $6750 by 4/15/17?  Also is the IRS notified when the FSA is closed by company FEIN or individual social security numbers? Thank you - this is confusing.