I received a letter in the mail informing me the irs needed me to verify my identity. I followed the instructions online and it wasn’t able to verify me. Help.

I followed the instructions to verify online and they couldn’t verify me. I tried calling the phone number listed on the letter but it keeps telling me to try again later. How do I resolve this?
They were able to verify my husbands identity with no issues. Why can’t they verify mine?