MBP 16 / Catalina - *all* web-browsers fail to open new pages after a few hours use.
I am experiencing the weirdest problem that I've seen in using Macs for nearly 20 years.
I have a late-2019 MacBook Pro 16 with the latest version of macOS Catalina (10.15.4).
The problem is this, which started about 3 weeks ago.
1) After a reboot, everything works as normal, but after "a few hours to a couple a days" (i.e. 4 - 48 hours), all of my web-browsers (Safari, Chrome & Firefox) fail to connect to "new" web pages, but pages already open continue to work normally including links to other pages with the same web site.
2) The problem seems limited to the actual web-browsers themselves, and not other internet connected clients. So Mail still works, Slack and other chat applications work, Spotify works OK. Other devices on the same network are all OK.
3) Command line network utilities still work and connect to websites, e.g.
curl, telnet, ping, wget, netstat, nslookup - all work perfectly with DNS names or IP addresses.
4) I have disabled firewalls, anti-virus web protection, and checked by any router controls - everything works as normal
5) I have tried different networks and ISPs, i.e. changing to different wi-fi networks and connecting to the internet via mobile data rather than fixed line. No difference.
6) I've reset PRAM
The browser failure is curious because it is only partial. Let me explain...
If I have a web page open, for example cnn.com, it continues to work, and links within the page to the same domain (i.e. cnn.com) continue to work as usual.
However, if I try to open a new tab and go to *any* web site, using DNS name or IP address, then it just hangs.
If I try to navigate to another page from a tab that is still working, e.g. go from cnn.com to bbc.com, then it fails. So it looks like "new" web domains are rejected, but ones that are working on an open tab continue to work.
I thought this might be a DNS issue, so flushed the DNS cache with:
sudo dscacheutil -flushcache; sudo killall -HUP mDNSResponder
No change.
7) The browser problem eventually affects system stability and causing multiple applications to hang. Generally I have to do a hard reboot (holding down the power button).
8) I have run two different virus checkers doing a deep scan.
9) I have reinstalled MacOS, but kept my data, so the only next step would be a complete new install which is very time-consuming given the number of applications I need to re-install and configure - and with no guarantee that this problem won't happen again.
The only applications that I recall installing before seeing these problems were Skype For Business (now un-installed) and GoToMeeting.
The Fact that command line and non-browser internet tools still working normally, but *all* browsers have the same problem is really weird. Are Safari, Chrome and Firefox using a common MacOS component (WebKit?). And how would this affect other non-browser client over a matter of hours or days?
I'd really welcome any suggestions of what to try...
Thank you!
John.
