Perjury is a crime. There is no conspiracy to commit perjury in US law. When in the last 5 years did Comey or Brennen testify before Congress? You have to show an overt act in furtherence of the crime to prove conspiracy.Since then Brennen, Comey, et al., have testified before congress repeatedly--as one example. During their testimony it is no clear they were lying their asses off and there's now documentation proving it.
If denial of a crime is conspiracy then everyone involved in Jan 6th attack on the Capitol can be prosecuted for conspiracy. All were involved so if even one person denies it was a crime. (Trump just made them all conspirators.

Of course, I suppose they could change the statute of limitations and retroactively apply it like New York state did to Trump--twice--to get convictions...
NY didn't change the statute of limitations for crimes. They tolled the statute of limitations due to Covid. It wasn't just New York that did that.