Update Problem -> Certificate Issue - Cannot Detect Proxy Settings

DELL Precision 7520 laptop running Windows 10 Pro (version 1803, build 17134.556) 64-bit.
CPU is intel Core i7; GPU is Intel HD Graphics 630 & NVIDIA Quadro M1200. Both WiFi & Ethernet.
Latest updates installed are: KB4023057 (failed several times); KB4462157.

Problem is that a certain web site with a certificate-secured page cannot be accessed by EDGE, IE, CHROME or FIREFOX. It WAS accessible prior to failed update(s).

Network Troubleshooter reports:
"Windows could not automatically detect this network's proxy settings."
(pane on right shows 'detected' and a yellow triangle with ! inside)

HOWEVER, I can start VirtualBox and launch a UBUNTU 18.10 VM and access the desired page with FIREFOX.
ALSO, this page is accessible from numerous other machines including Win10, Win7, UBUNTU, etc.
It's clear to me that this issue lies within WIndows 10 on this machine only!

I attempted SYSTEM RESTORE from two most distant RestorePoints but both failed, even after disabling the Antivirus product I run on this machine (BitDefender).

I can of course restore the hard drive image as it left manufacturing but that leads to a whole bunch of work.
I don't start this laptop every day; indeed, it may sit idle for a week or more between boots.

It's clear to me the problem lies within windows networking but after that, I give.

I'd be grateful for any suggestions as to how to cure this issue.

Welcome to the forum the clue is detect this network's proxy settings check all your browers as they must be using a proxy server not going directley to the internet. This can be caused by malware or anti virus software that sets up a proxy to scan incoming files. Have you installed or removes any security software?

Nothing has been installed save µsoft updates! I always let Windows automatically detect the proxy settings.
I've NEVER used a proxy server.

It should be set to network not a proxy it cant detect one if you havent got one hence the problem

I've been in contact with DELL support but we haven't nailed it yet.
Microsoft support seems to re-direct to azure which seems to be in the ditch today.

Have determined that the mouse successfully pairs and connects with another bluetooth laptop (Latitude D630) and functions nominally. It pairs and connects with the Precision 7520 but can't get mouse data to PC.

Furthermore, a Samsung Galaxy S7 with bluetooth enabled can pair and connect to the Precision 7520 BUT cannot transfer data - just like the Mouse. I'm concluding that something's broken in the Precision 7520 but I have no clue what it might be.

At the moment, I'm forced to use either a USB or a Wireless USB mouse since touchpads are an abomination to me.

Ideas anyone?

We're did mouse come into the equation we were sorting network?

One of my alternatives was a "Factory Refresh"; I chose that to save time and it broke bluetooth but drivers solved that and I'm back 100% functional. DELL support was very helpful.