Unable to use MarsEdit with Blogger - Google web OAUTH failure with DHCP mode on AirPort Extreme

I'm now unable to use MarsEdit with Blogger on Mojave or High Sierra. When Google asks me to authenticate instead of getting the usual embedded web page for entering credentials I get a blank page.

Either Google has changed something so this only works on Catalina or there's something odd about my Google accounts. I've tested with

• two non-2FA Google Apps identities that used to work
• my personal 2FA Gmail Google ID
• my wife's personal Gmail Google ID never used for blogger
• two user accounts on my Mojave machine
• 1 user account on High Sierra
• Admin and non-admin account
• Clearing caches with Onyx
• I think I also tried an older version of MarsEdit that was on my old account on the High Sierra machine

macOS Console has not been helpful, but I have yet to download and try it using Consolation.

 

MarsEdit dev (Daniel Jalkut) says it works for him on Catalina and on pre-Catalina.

Update 12/6/2019: I eventually realized the problem was my home network. I have a Comcast Xfinity router and an Apple AirPort Extreme. Both have had no configuration changes in months, but Comcast recently updated my service and the AirPort firmware went to version 7.9.1 a few months ago.

 

Inquiry on Apple Discussions.

 

Update 12/7/2019: Today I discovered my AirPort Extreme Guest Network no longer works. That’s the network all our IOT devices connect to.  Turns out suggests that the Guest network doesn’t work in Bridge mode unless the internet router is configured for VLAN support. Would be nice if Apple documented some of this stuff. Maybe this is why they exited the router business.

 

So I have to go back to double NAT for now then try reverting the firmware. (Though once I’ve authenticated a blog I don’t need the web OAUTH, so there is that option.)

 

Update 12/8/2019: So I reverted from 7.9.1 (79100.2) to 7.7.9 and it still doesn’t work! So I think I’ve ruled out a problem with the AirPort Extreme firmware update. I think I tried an older version of MarsEdit. I can’t say for sure but now I suspect it’s something Google did that broken compatibility with Double NAT (DHCP) on the AirPort Extreme.

 

I went back to 7.9.1 (got an ominous notice that firmware update failed but it seems fine) and I guess I’ll use my TunnelBear VPN when I need to authenticate with Google. I’ll test periodically to see if Google fixes things.

 

I tried out Google OAUTH playground. It’s a bit above my pay grade but it seemed to work across my Double NAT setup.