This appears to be a TurboTax error, and a blocking error that will prevent many filers from completing their return.
If you entered Assets in your 1040 Sch. C, which happen to add up to zero depreciation, this information passes the Federal review and is imported into the state return.
Turbotax *automatically* adds that zero total to Form 568 line 17a. During state review, you are advised that zero is not permitted *even though Turbotax added it*. Furthermore, Turbotax disabled the field you need to change in that review and correction process, and further denies any attempt to remove the zero from that blank (contradicting their explicit instructions).
This is a big problem that TurboTax must solve or it will wreck filing for many affected customers.
