My search shows that the tax law has already been approved for 2018 to deduct mortgage insurance premiums, but your site does not, which prevents me from filing. Why?

You need to search the IRS website for accurate information.  There are tons of inaccurate websites out there stating that the PMI deduction has been extended, but it has not.  If you notice the dates on those articles they are all from October 2018 and earlier, before anyone knew for sure what would happen.

Read IRS Publication 936, it was updated as of Jan 24, 2019 and it shows that the PMI expired in 2017.