Solved! Laptop keeps disconnecting from wifi, only when "extender" is connected

[flayer6]

I have one laptop (HP) that won't stay connected to wifi. It worked yesterday until I installed a new router/modem. All other devices unaffected. Here's my new setup:
New Arris SBG7400AC2 router/modem connected by coax. 2.4 and 5 have channel auto. SSIDs: Work, Work5G
DHCP range: 192.168.0.2-192.168.0.249
IP (gateway): 192.168.0.1 255.255.255.0

Older Netgear C6300 connected to Arris (wired). Turned off Use Gateway as DHCP Server
2.4 channel is auto and 5 is set to 157. SSIDs: Amp, Amp.5G
IP: 192.168.0.250 255.255.255.0

HP IP currently 192.168.0.4 (obtained auto)

With all equipment, I can ping both IPs successfully. With HP, I can ping .250 successfully, every time. I fail 3or4 out of 4 times (request timed out) when pinging .1, with HP.

I was thinking, must be internal NIC or settings on HP. So, I tried ipconfig release, renew, flushdns, various netsh commands (i i r r, winsock reset, etc.), making sure computer can't power down wifi, made sure on private network, forget network, turned on connect automatically (to each SSID individually, one at a time), lowered roam to Medium-low (so wifi wouldn't try to bounce from one SSID to another), turned off Hotspot 2.0 networks, set obtain DNS automatically and tried using Google's DNS (8.8.8.8, 8.8.4.4) and the list goes on. Ran windows network diagnostics. Performed Network reset. Uninstalled, reinstalled, and rolled back drivers. Even ran AVG full/deep scan. Rebooted after each step.

I've unplugged, waited 30 seconds, plugged in both Arris and Netgear. I went to Spectrum web site and did a reset that way.

Here's the kicker; the HP is fine, if I disconnect power from Netgear! I can connect to Work or Work5G and browse away like nothing is ever wrong. With HP, I can ping .250 successfully, every time AND I can ping .1, with HP successfully every time.

As soon as the Netgear is powered up, the HP connects, allows me to browse slowly for about 1 minute, then I get server not found errors, can't reach this page, etc. using Chrome, Edge and Firefox.

All other devices use the Amp or Amp.5G to connect, as they had in the past, so I never had to reconfigure any other devices.

I'm at my wit's end. Any help, suggestions or configs you can suggest, would be much appreciated. The HP has no Ethernet port, so a wired connection isn't possible.

 

[helpstar]

try connecting to the AMP SSIDs

 

[flayer6]

try connecting to the AMP SSIDs

I know I put a ton of text in my question but I meant to say that I had done so, when I said "turned on connect automatically (to each SSID individually, one at a time)". I connected to each SSID and always get the same results.
At the end, when I mentioned, "I can connect to Work or Work5G and browse away like nothing is ever wrong", is only when the Netgear (with SSIDs Amp, Amp.5G) is unplugged from power.

 

[helpstar]

any tools like 3rd party firewall or antivirus installed? uninstall and test without it

Windows firewall is set to private and not public for the networks?

the extender´s firmware is up to date and the bios of the laptop as well?

 

[flayer6]

any tools like 3rd party firewall or antivirus installed? uninstall and test without it

Windows firewall is set to private and not public for the networks?

the extender´s firmware is up to date and the bios of the laptop as well?

Uninstalled AVG Free Virus Software and it worked immediately and continuously after reboot! Thank you so much for the suggestion!!! I'm truly very grateful.

Any idea why that helped, as I always had AVG, connected to Netgear with same SSID. Only difference was install of new Arris modem/router.

PS: reinstalling AVG to see what happens next

 

[helpstar]

Just a guess:
Antivirus software has a network detection implemented which can restrict the connections to only use "known" networks. This can lead to false alarms or the known network can be restricted after an update, if the user doesn´t click on "i trust this" or the software is restricting it automatically to protect the system from the outside world.

 

[flayer6]

Just a guess:
Antivirus software has a network detection implemented which can restrict the connections to only use "known" networks. This can lead to false alarms or the known network can be restricted after an update, if the user doesn´t click on "i trust this" or the software is restricting it automatically to protect the system from the outside world.

BTW, reinstalling AVG made the issue appear again, so I uninstalled and I'm using Win10 native protection.

 

[helpstar]

I´m using Avast free antivirus
but win10 is fine too