Ok, I think the website asks whether you've been out of the US in the last 5 years. If you answer "yes", and then "yes" to question whether it was more than 6 months, you get a question whether the USC spouse was in the army, working for the US government etc. If you answer "no" to that, then the website thinks you're not eligible.
So... Maybe filing on paper is a better option or you wait for 5 years then online system will be happy 😃
So here is the thing, IO may also think you're ineligible because you broke continuous residence in the last 5 years. You should be OK, and the lookback should be 3 years if applying under 3 year rule, but I'm not a lawyer.
@PJMERK did you have a reentry permit when you left? Did you keep assets (property, bank accounts) in the US while you were away? If no ties were maintained, with no reentry permit technically, USCIS can conclude that you abandoned your residency and attempt to strip you of your LPR status. It won't be fast and the likelihood of this is miniscule, but there's still a chance.