I agree, it is an odd restriction, as I can see other use cases besides the membership websites where the 1-year term limit is a deal-breaker.  

Seams to just be the trend. For example latest PayPal APIs has the exact same limits. There's fewer and fewer providers that will allow payments over 1 year. My best guess is it's some sort of liability/consumer protection thing. There's a few janky workarounds for this like abusing free trials or in the case of Stripe abusing subscription schedules, but it causes really weird billing behaviors. For example to get this to work with Stripe we'd have to do the following and for PayPal there flat out isn't a workaround.

Subscription Schedule
Subscription 1
- Price: Full Price
- Duration: 10 Days
Subscription 2
- Price: Free
- Duration: 1 Year
Subscription 3:
- Price: Full Price
- Duration: 1 Year

That's how it'd work if the subscription was 375 days for example. On the 3rd subscription in the schedule it would exit the schedule and lock into that recurring billing. The first subscription cycle is billed in full on subscription 1 with subscription 2 dealing with the regular cycle. While this can work it's not really the intended behavior of subscription schedules. We're already using subscription schedules to deal with subscriptions that have different initial price/duration compared to recurring price/duration so it'd result in a conflict with that existing behavior. It's basically a nightmare scenario to do the above.

There's probably alternatives like to take the extra days over 365 and push the start date of the subscription at Stripe, but then they won't be billed until those extra days have finished, which is fine if it's like 1 or 2 days, but a disaster if it's too many. I'll continue to explore possible workarounds, but unfortunately the easiest approach is to just not allow recurring beyond 1 year.

Correct me if I am wrong, but when the membership comes up for renewal next time, they can then choose the recurring option since by then it truly is a 1-year term.  

Yup, they should be able to as long as it's not greater than 365 days.

Check the notification for their renewal in CBSubs > Notifications and for any errors during the renewal in CBSubs > History Log. It's hard to say what could have gone wrong as we've massively updated the Stripe gateway since then to their latest APIs and guidelines.

As for forcing a subscription back into an auto recurring state edit it from CBSubs > Subscriptions by clicking the # under the ID column. Next set the following.

Autorenew Type: Mandatory
Autorecurring Type: Autorecurring with notifications
Previous Autorecurring Type: Not autorecurring

You can also reactive it from here as well by setting the following.

Status: Active
Previous Status: Expired

If there are no errors please PM backend super user login credentials and will take a look. Please include details regarding what user this happened to so I can dig into the logs.