As the ratification window was closing in 1979, Congress decided to extend the window to March 1982. Rather than use the amendatory process, which requires a two thirds vote of both Houses of Congress, it chose to use the legislative process, which requires only a majority vote of both Houses and signature by the president. Jimmy Carter doubted the constitutionality of this method, but he signed the extension anyway.
In NOW v. Idaho, the federal courts got involved and declared that Congress used the wrong method to extend the ratification window. What Congress did was unconstitutional. Congress should have resubmitted the amendment proposal to the states for ratification by starting the whole process over from scratch, with a two thirds vote of each House to send it to the states for ratification.
Appeals to higher courts failed. The Supreme Court refused to hear the case because by then even the 1982 window had expired. The lower court decision in NOW v. Idaho stands: the ERA died in March 1979. Ratifications by Illinois and Virginia don't count and are just virtue signaling.
Thanks for that educational response. I was not as informed about amendment procedures as I should be. I didn’t give the ERA amendment much thought because there had been almost no discussion of it in my lifetime. The extent of my knowledge about the ERA was that it was “frozen” because not enough states had ratified it. I actually did think that it could be still ratified if more states did so.
I’m so thankful I know better now.