My suggestion is basically that if someone accidentally can't pay for Nitro for some reason they should be able to reclaim their streak. For example, their card was declined because something is wrong with it, or they don't have money for it at the moment. Or maybe around the time their card expires, they have to cancel/ freeze their card because of fraudulent activity and need time to get a new one.
Basically, mishaps happen and as a result, people can lose their Nitro streak. My suggestion is if they reactivate their Nitro within half a month, or maybe an even more generous 1 month, there could be a button shown in the Nitro tab that they can click to restore their streak if they wish to do so. Or maybe it could be a button that automatically creates a ticket for them that they want to reclaim their streak and it hasn't been a month yet.
So yeah, that's basically it.