Mailed return in limbo (not delivered) -- what to do?

Using the Turbo Tax desktop software, I filled out my state tax returns and mailed them, USPS certified. My CA return's USPS tracking has been showing the status "In Transit to Next Facility" for almost a month, though it did make it to Sacramento (delivery city). I'm due a couple thousand dollars refund from CA.

 

I'm worried that the envelope may be lost. Even if just misplaced, the refund delay is annoying. What do you all recommend I do at this point? I could file electronically after all (paying the $20 extra fee that I guess I should have done in the first place -- could I get USPS to cover LOL?), but will that be problematic if my mailed return does eventually get delivered? And/or can I ask USPS to look into it? Any other ideas?

 

More details on mailing in case it helps: Of the three items I mailed certified that day, two were delivered within a few days. (One was my other state return since I moved last year.) The third, my CA return, made it to the delivery city Sacramento CA in a few days and was marked "In Transit to Next Facility" a few days after that, and its USPS tracking status has now been unchanged for almost a month.