WiFi disconnect and can not find existing, previously connected WiFi

[laray]

Downstairs Tstat offline, can not reconnect to WiFi.  No Wifi networks show when scanning.  Reset tstat, rebooted router.  Tstat upstairs works fine.

Voltage/battery all good.  has c wire connected.

Cooling still operates/regulates properly but no walk up presence.  Have to tap it a few times before screen appears. 

Corrupt firmware update?  Any way to manually download and install firmware using the USB connection on rear of stat?

Stat is about   two years old, has no previous issues

[David_K]

Check for a W5 error code:
Troubleshoot a Nest thermostat w5 code - Google Nest Help

[laray]

Thanks, but  no W5 error code plus I have already reset the stat to factory def.  Never seen that code displayed in the network settings

[David_K]

Good to confirm. You mentioned having already tried some steps. Does that include all the ones listed here?

Nest Thermostat Troubleshooter

[laray]

Yes, tried all steps.  Still not able to find wifi network.  Seems too be an issue with radio inside stat.   Replaced stat.  Once old stat removed, the battery went dead within 5 min on the old stat and shutdown.  Never saw a low battery icon.  Could have been part of the issue.

Anyway, thanks for the help.   I have three other stats (for several years) in other locations and homes and have never had this issue.