Notice of deficiency CP3219A Retirement Income was reported by "Retirement Services" Do I refile 2020? Can the penalty get wavied? Are there IRS payment plans?

I recieved a notice of deficiency CP3219A
Increase in tax (deficiency) $20k
Substantial tax understatement penalty $4k

December 2019 I switched employers and had a 401k loan.  Both of my employers utilize Charles Schwab and the 401k was rolled over.     During the pandimic with the Cares act I withdrew additional funds form the 401k.  
I was understading all of this was covered in 2020 tax, however I recieved notice of deficiency CP3219A
Retirement Income was reported by "Retirement Services"

I am not sure where to start.  
Do I refile 2020?  
Can the 4k penalty get wavied? 
Are there payment plans with the IRS?  

Thank you