@tomr70 had a very helpful response. I spent about 10 hours on this and spent probably 5 of those hours on the phone with TurboTax. I don't have a perfect solution, but here is what I did and some insights in case it's helpful. As an aside, TT is horrible software with very poor customer support, so this is definitely my last year.
Some insights:
1. This is 100% tied to crypto transactions, and the "unable to print" error is tied to the "server error" when submitting the e-file. The CS agents insist that you restart your computer, clear your cache, and that they have never, ever heard of this problem before. I swear, by the fourth person telling me to delete my cookies I was ready to lose it.
2. Removing all the crypto transactions from the return allows you to print the page.
3. However, unlike for @tomr70, the CoinTracker solution did not work for me. For me, adding *any* crypto transaction threw the system into the cannot print/cannot submit loop. The one CS person I had who was super helpful and stayed on with me for several hours told me it was because the CoinTracker spreadsheet had the 4,000 transaction "embedded" inside the CSV file, so even though it looks like 29 lines it still contains all the data. I do not think that is the case but she was quite sure about that.
4. However, after deleting all crypto transactions (and thus being able to print and pass review) I was told to manually enter the 29 lines from the CSV file. This did not work either. In fact, entering a single transaction (i.e. "Bought $10 btc on 1/1/2021 sold for $20 on 1/2/2021" triggered the error again and would not allow print.
5. Suspecting there was some remnant from my API integration before I switched to the CoinTracker method, I decided to just start over. However, and extremely frustratingly, TurboTax doesn't allow you to start over. Literally, when you try to delete and start over, a dialogue box pops us saying, "You cannot start over. You cannot delete. We own your soul forever." (Ok, not the last part, but basically)
6. So, I could not start over, I could not print, and I could not submit. Pretty awesome!
7. Eventually, they gave me the desktop system. I was able to print from that, and view the forms directly. I printed the state and federal and drove to the post office and mailed them.
In the end, this issue cost me about 10 hours and $50. And a lot of sanity.
