H500 does not turn on

https://www.hayward-pool.com/pdf/manuals/H-series-H100ID1-ABG1001.pdf There is a wiring diagram and some troubleshooting information here.

Updating firmware is always a good start. My question would be, is it losing satellite contact due to positioning or surrounding materials blocking the signals from one of the 33 satellites that make GPS work.

I sounds like the battery is not holding a charge. You may need to replace the battery soon. The beeping typically indicates a low battery

The battery has lasted at least 8 years. It has reached its end of life. There is no battery that lasts forever.

It's eight years old now, and if as you say it has had intermittent use, then the battery will probably have died unless charged at last once a month.

Hold the phone button down for about 4 seconds.. The light should blink 2 times and then stay on to add device to your phone once connected light will go out...Hold button down again light will blink 3 times and go off...........

sounds like the coils inside the air handler/furnace are freezing up. likely cause is the freon charge is incorrect (probably undercharged). it may have been correct when the tech did the work but some may have leaked out. it is slightly possible too that the system is overcharged. you should have the system pressure verified, and then have it checked for leaks.

After I posted my problem, I tried one last thing, I "rebooted" my phone; turned it off then back on.
After I did that everything worked fine.

don't know if this will help,

I had this same problem a couple of months ago, battery appeared to be charging but got emptier and emptier, tried different chargers and no improvement etc.

Friend has same phone, used their battery in my phone which was charged and phone was working fine, meanwhile, charged my battery in their phone and it charged fine and then for 2 months no repeat of the problem...

then last week, it happened again, trouble is this time i'm on school holidays and can't use the friend's phone for another 3 weeks!

had same problem i found just turning my phone on and off to solve the problem
hope it helps