If you scroll down near the bottom of this thread, a PTO user said that it saves as you go (like Turbotax Online)...you are using Proconnect Tax Online and not one of the ProSeries versions, right?

https://proconnect.intuit.com/community/proconnect-tax-online-discussions/discussion/does-proconnect...

I just spent the last three and half hours entering client information for form 1120. Went to look at a preview of the return and the entire thing was blank. Thought maybe it was an issue with the preview, so I looked back at each page where the data had been entered and indeed every page is blank. How could Intuit let something like this happen? Can I get this information back?

Contact support either via phone or chat to discuss this issue. https://proconnect.intuit.com/support/en-us/help-article/intuit-account-settings/contact-proconnect-...