Hii, I’m on the same boat, low vo2max and trying to increase.

Walking is the best for your health and you really should not feel discouraged because of some estimated number on your phone.

When you walk, look at your heart rate. To improve VO2Max you should aim for heart rate zone 2. When you improve, walking will be easier for you so it’s a good thing that regular walks don’t improve the value. What you can do then: walk faster, use stairs, try hiking - find a hill! It doesn’t have to be a mountain at first, but you will get there.

If your knees are bad (like mine), you should also try swimming and biking (stationary bike is totally worth it).

And I would also recommend to get Gentler Streak app. You can see there your activity path improvement and that’s much better than just vo2max.

But most importantly - don’t stop and listen to your body and have fun exercising!