How do I file an extension for my 2017 California state taxes?

[DoninGA]

There are no extensions for a 2017 tax return.

[VolvoGirl]

Or do you mean to now file a return you had on extension?

Did you use the online version for federal?  

How to finish a prior year online return

https://ttlc.intuit.com/community/prior-year-return/help/how-do-i-finish-a-prior-year-return-that-i-...