The only other thing I can suggest if not tried is to delete the 1099-R and enter the IRA contribution without the conversion to make sure that part works and then update it and put in the 1099-R in.
i feel like you’re flying blind with the online version I’ve seen a lot of posts here about the behavior and cost. The desktop version is a lot more flexible to dig into forms and details at any stage. Desktop is not without issues there seems to have been some downturn in technical quality this year and redesign of the 1099 input, but you could consider switching to desktop. Not sure prices on Amazon etc but it was discounted there more than intuit directly. No guarantee of different outcome but I think it will be easier to troubleshoot and be confident in the return.
I’m not a CPA/expert but what you’ve described this sounds like correct backdoor roth, which works for people above the limits to contribute directly. One pitfall is not being eligible to make the nondeductible contribution to the IRA to start with, which can happen if you don’t have “earned” income from W2 etc.
