Apple Watch no longer registers exercise

My watch (Series 4, latest OS update) has stopped counting (almost) anything as exercise. Is there some way to fix this?

In detail, we've been going on long neighborhood walks since starting to work from home in March. The watch has generally counted most or all of those walks as exercise. Then we had about a month of smoke and couldn't go outside, so any exercise I had was on an elliptical machine. Now that the air is good again and we're out for walks again, the exercise ring never moves off zero. I've tried outdoor walk (which was working fine before) and inside walk, both never move off zero. Heart rate and pace are basically the same as when it was working fine, so something has changed with the watch. If I use "Other" it will register, but then I get no distance information. Suggestions?

[Re-Titled by Moderator]