@Nstanton62 

I tried to include links to some of the references but it was disallowed Trying again:

  @Riley_S thank you for the comment.  Yes this is 2.4G only device.  I had tried what you said - disabling and/or not broadcasting all but the RE315 2.4G band.  The muQ device saw it, my iphone was on it when installing the device, and it still would not connect.  I also did a factory reset on the myQ device to completely uninstall it, then reinstalled from scratch.  It still would not connect through the RE315.  I unplugged the RE315, installed it through the AX73 with a very weak signal, then repowered the RE315.  It would not switchover to the RE315 like other devices.  My iphone connects seamlessly to the RE315 and it has good signal and internet.  I do have a ticket now with TPLink support and am communicating, but hoping the forum community might have others withsimilar problem that found a solution. 

  @Riley_S Very helpful info thanks. I had seens those steps before but not in the concise list form.

• 2.4G is enabled
• 802.11 b/g/n is enabled as far as I can tell.  In Smart Connect mode you cannot specify and I believe b/g/n/ax is enabled by default.  I had tried taking it out of smart connect to ensure it's on the 2.4G band but did not change to b/g/n only
• DHCP is enabled thought I did put the RE315 as static IP so I have a consistent IP from my desktop for admin
• security is WPA2-PSK
• Not sure about port 8883.  I saw that in other discussions and on Chamberlain website when troubleshooting.  I'm fairly tech savy but have not been able to confirm the port is open.  What's confusing is it connects easily to the AX73 main router but will not to the RE315 under any circumstances I tried. My other myQ opener also is connected to the main router (better signal) with no problem. If a port problem wouldn't that be on the main router?
• No MAC address filtering in place.

I did read something that indicated the RE operates in proxy mode which changes the MAC address to the main router.  Again I'm no expert but that sounded suspicious in that myQ may be looking for the original MAC address in it's database?  https://www.tp-link.com/us/support/faq/927/ 

Best,

NStanton

  @Riley_S BTW when going through the myQ device setup through the RE315, I get solid blue followed by no light, which myQ says is  the opener was unable to connect to your home Wi-Fi network.

  @Riley_S The only IP I made static was the RE315 so I didn't have to hunt for the current IP when wanting to connect for admin from the desktop, if that makes sense.  I have since changed it back to dynamic so evertything is basically default as it would be set up automatically in OneMesh mode.

I never got far with manually opening ports.  I tried a quick change following something I saw on another post, then tried a "test my port" website, but it never showed open.  I would have to learn more about specifically how to open ports on my new equipment here.I do understand how the proxy retains the last half of the OE MAC address, but I never did antyhing on filtering or white/blacklisting other than look at it.  I just wondered if the myQ "portal" in the cloud? looks for the native MAC address of the opener, which is associated with the serial number that you also must enter, in order to authenticate.

  @Riley_S That myQ chart is deceiving.  Read further on the solid blue light and it says "When there is a solid blue LED light on the Wi-Fi garage door opener, the opener was unable to connect to your home Wi-Fi network."  It does suggest checks on phone settings, which I did, but it's definitely the step where it uses the phone app to connect to the network.  It gets all the way to showing what networks are available, mine is there, I input password and click to connect, then it spins for a while, comes back saying it can't connect and the solid blue light goes out. Definitely solid blue though - I stared at it about 50 times!  

I did forget the home network and reset factory defaults on the opener which completely removed it from the myQ app.  I then restarted from scratch like when I first got the opener a year ago.  Dame issue not connecting.

I agree on the port opening - that seems a little deep for what I want and should have to do.  All VPN and private setting are default as automatically configured when I started up the router and RE new.    

Again, the puzzling thing is everything works great as intended except trying to connect it to that darn range extender. Works fine connecting to the main router AX73, just a very weak signal due to distance and obstructions, which is why I got the RE.  Also does fine with the TL-WA801ND I've now set up an access point outside of one mesh a little closer for a better signal but still weak.