Max heart rate auto detection

The formula is likely the least accurate and useful metric imaginable.  Forget it.
Are you using a HR strap? If not the optical reader isnt great at determining it.

Your best bet is to do a proper test - repeat hill sprints to get your actual max HR.  Running like mad isnt it - it needs to be absolute max effort you can sustain for a few seconds or so.  Wont work on the flat or a normal run.  Caveat here is if you're asthmatic, speak to a doctor first.

That said, for pace zones its not as useful as lactate threshold either.  Much better off setting max HR then working out the lactate threshold and basing all your zones on that.

You may be overtrained, and when you are fatigued the achievable MaxHR drops quite a lot, even 10/20bpm, it's normal physiology.
Then, the formula 220 minus age is just a general reference and can't be trusted entirely, for me at 43yo formula would suggest a 177bpm MaxHR, but I can achieve up to 189bpm in a bike race all-out sprint finish. Everyone has variations.

Thanks for your response! I gave up on the HR strap because it was so similar to my watch it wasn’t worth the effort to put it on.

I might have to give it another try.

Well, you should use the HRM, especially with a maxHF test.
MaxHF is individual and it's age and genetic based.
You could use a calculator like here:

https://www.cactus2000.de/de/unit/masshrt.shtml

But consider that the real numbers could differ by 15 to 20bpms

Or you try some test mention here:

https://theathleteblog.com/calculate-max-heart-rate/

Here you should also consider that you have to go to you limit. As mentioned in the blog it happens often that the participants break the test before they reach their real limit.
I always say that you've to go to your "vomit boarder" and that is not so easy, and maybe need some tries.
Have a eye on you're regenerated, sleep was well, HRV is in a high range and your mental load is good.
But at the end it is it worth it, because with the right maxHF the training is most effective

Thanks so much for the info! I am starting to think I just hit another hurdle in my fitness. When I started it was hard to walk the recommended amount of time.  Then it got easy. Lots of progress! Then it got to the point where I couldn’t walk fast enough to keep up the recommended pace.  It would hurt my ankle due to taking long strides (I had ankle surgery a while ago and it limits what I can do).  So, I switched to jogging which believe it or not was better for my ankles but my heart rate would shoot up and I had to slow down and walk.  So, I would jog a bit then walk a bit.  I couldn’t keep up the recommended pace and keep my heart rate in the correct zone.  I switched to heart rate based workouts and then that worked to the point where I could almost jog my entire route.  I only walked when a hill would push my heart rate up. 

Now it seems my heart is doing much better. My VO2 max says it is in the green! Now I am able to exercise in a way that my legs are feeling it. Before it was always my heart rate was the limiting factor. Now it seems my legs just can’t keep up. That and I am having trouble coming close to lung limits (especially with the cold weather and my stress induced asthma which isn’t terrible but definitely something to keep an eye on). 

I can move pretty quick in the beginning to get my heart rate up.  My base workouts seem good and my tempo runs seem good. The problem arises with my threshold runs. I can’t push hard enough to get the heart pumping without feeling like I can’t  maintain that level for that length of time. 

would you think it better to do the Threshold run to the best of my ability and fail to maintain heart rate, or would it be better to skip threshold and do more base, tempo, and long runs?

The optical rate isnt good at picking up rapid changes and spikes.  As such its pretty good in a long endurance run and no real difference to a strap.

Where it fails are sprints, intervals and max HR stuff as it cant react rapidly enough to measure the spike - it just averages and reads low.

You're welcome
Well, it's not easy for me to give any recommends because I don't know you, your experience, physic, body weight and so on.
I'm now running since 45 years and realized something for my self namely that ego running or everything we do to satisfy or ego is actually a disadvantage.

I would work at my basic endurance, means, you should be able to run for 90 min in the Zone 2 (green) area further I would follow the daily training suggestions incl the thresholds.
Patience and consider everything need its time. We can't expect super fast changes especial if there are factors like tendon, ligament and so on are involved. It need its time.
Be patient and enjoy running, that is message I can give you. Cause even without to know your 100% mxHF it's healthy and good for you.

Well thanks for the advice!  I know it is a long term thing and I can’t take shortcuts.  I was just a little worried that I was accomplishing everything my watch was telling me but all of a sudden I could no longer keep up.  I will try to keep going as best I can.  My only rush is that I am not sure how long I can keep running.  My knees ache.  Overweight and 52 and haven’t run since I was a kid even then I had 0 endurance.  So, I am hoping my knees hold out long enough to lose enough weight that it hurts my knees less. Might have to switch to riding my bike.  The watch doesn’t seem to cater MTB as much.  Seems like I need a power meter in order to get daily suggestions.  Anyway, l will try to keep going as long as I can.

Your muscles and stamina will improve faster than your joints. To reduce the load on the joints, you can walk uphill instead of running flat. At least be very careful with downhill. Bicycling is alto very nice for the knees. And remember you can decide the training yourself without suggestions from your watch.