I got a similar notice from CA Tax. I used their chat feature on ftb.ca.gov.
I did not have an account on their web site, so I had to wait about 5 days to get a PIN (via USPS mail) to complete my account, before I could go further. Once I confirmed the account with the PIN I was able to use the chat, during business hours only.
After a 20min waiting time, I was connected to an operator. After few verifications, the operator asked if I was in position to upload my W2s within the next 5min. I did the upload, the operator checked the numbers and cleared my account.
For this issue, I say the chat is the way to go, just make sure you have the W2s in a file ready for upload. And you account for the time to get the PIN via mail.
