Why doesnt it apply? Did they sell the home? Did they fill out the 5405 in that year of sale showing that its been disposed of?
You may want to use the IRS FTHBC lookup tool and see what IRS has on record for them
Like @Just-Lisa-Now- asked, did they sell a home in 2019? If yes, is this triggering the First Time Homebuyers Installment Payment rejection? There is a check box on Home Sale Worksheet for transferring info to Form 5405. I'd open Form 5405 and then delete it, just to make sure no data is populating the form for some reason.
After further looking into it (as the others helped you with), if you still think it does not apply to your client you would need to file by mail. Tell the client they will receive an IRS notice about it, and prepare to defend your position that it does not apply.