@Harley75 

If you split the devices, some on the 2.4G and some on the 5G are you seeing the same thing?

Where there any other settings enabled/changed other than changing the SSIDs?

@Tony 

Thank you for responding ....

The 6 devices connecting on the 2.4Ghz require 2.4Ghz.  Several devices are the TP-Link/Kasa switches etc that only work on 2.4Ghz.  After pondering the situation I wonder if I should have let the AX3200 run for a while and maybe it would start working okay after the 6 WIFI devices made/ stabilized their connections.?.  I didn't wait too long before returning to the old router.  All in all this router should be overkill for our small home network.

What else changed from default?

LAN IP

DHCP scope range

Added several DHCP reservations

Added a NAT forward

SSID (the topic of this message)

I have to believe this AX3200 should not be this sluggish, really ever. 

I plan to reconnect and try again after reading some posts/thoughts from others and TP-Link tech support.  So far nothing from my email support ticket to TP-Link directly.

Update:

I started over with this new AX3200.  Did a factory reset to start as out of the box.  Stepped through my setup that included changing the LAN IP and modifying the DHCP pool.  I left the WIFI settings default.  Left the Internet port disconnected.  I tested WIFI by connecting my iphone with no issues.  I connected the Internet next, checked wifi and all remained okay now being able to get to the Internet.  I then changed the WIFI SSID to my "old" configuration and with no resulting issues with all my existing WIFI devices now able to connect.  Not sure what happened with my initial try, but my second setup attempt appears to be successful. 

@Harley75 

Thank you for the update. Glad it is working fine, but definitely odd. I would probably speculating defaulting it maybe reset something in the software that wasn't working right.