PSA: if you also forgot about or missed the Federal Tax Service switching to new digital signature algorithms on April 1, here are a few details.
If you have a RUTOKEN 2.0, you need to replace it. Buy a 3.0, or a Lite, or whatever the tax office recommends. They have vending machines with tokens there.
The 2.0 won't work with the tax service anymore, but there's a catch. You'll still be able to send reports from your accounting software with the old signature. But when the tax office sends a reply, you won't be able to decrypt it. So it's better not to rush sending anything, and get a new signature first. Especially since quarterly reports can still be filed for another two weeks.
I once again (in Russian) renewed mine at the Solnechnogorsk tax office, and as always, I recommend it to everyone :) But I managed to send a couple of reports with the old signature, the reply came almost immediately, and I couldn't decrypt it. I had to call the tax office to confirm that everything was fine on their end.