The first place to look is the documents you received during open season or soon after you signed up for the account.
I haven't run into a company that required an employee to put funds in. In fact one of the benefits of the program is that you aren't locked into $x a paycheck. You can front load during the early part of the year, or increase the amount withheld after you get a raise, or for any reason. The IRS only cares about the maximum amount you can deposit during the year, and how the money is disbursed.
It is possible that your employer makes a contribution to your account. I could see management only wanting to do that for employees that are actively funding the account. If that is the case there should be memos from HR/management explaining that.
It is also possible that the new HR person has confused the FSA and a flex spending plan. It is also possible that the company will be eliminating the plan for next year, and they were trying to tell you to make your deposits now, because you won't be able to next year.
If you can't find a minimum contribution mentioned in the documents/emails then ask HR for clarification. If there is a minimum then that number or percentage has to be written somewhere. Also if there was a minimum you would think that the system would automatically force the deduction from your paycheck, and there would be paperwork you signed acknowledging it.