I just upgraded to 7.10.2 (I’m not sure what I was on before, but it had been a fair number of months since I’ve upgraded).
Now my HAP AC3 won’t connect to my EERO unless I disable WPA3 PSK. I have other devices connecting to the EERO on WPA3 and the only thing that changed was the Mikrotik software upgrade.
Already tried forgetting the network and reconnecting again ?
There have been quite some fixes on the security parts and sometimes this is needed.
Or are you trying to go the other way ?
I didn’t think there was a “forget the network” option in RouterOS? What I did do was switch the SSID and connected it to a hotspot on my phone first to make sure WiFi in general was working. I also tried connecting to the Eero’s guest network and it had a similar connection issue. Basically, the Mikrotik client just doesn’t seem to want to talk to the Eero w/ WPA3 anymore.
I haven’t messed with downgrading yet, but I guess that is the next step unless there are any suggestions for fixes. I was hoping to try and get some detailed debugging information, but the Eero doesn’t seem to emit much and I didn’t get much out even with wireless,debug logging out of the Mikrotik.
There isn’t, that is an option on client device, and on windows devices you also have that option (don’t now for mac os)
Hence my question if you were going to other way 
I assume your AC3 is using wifiwave2 package ?
Correct! I am using WifiWave2 in Station mode.
And how did you determine the required settings ?
Can you use scan / connect to make connection to EERO ?
I’m not sure what you mean by how did I determine the required settings. This has been a working configuration for a long time (year?) until I upgraded router OS to the newest version (I’m guessing it’s been 3-6 months since I last upgraded). Before I had WPA2 PSK and WPA3 PSK selected and it would connect using WPA3. Now, when WPA3 is checked, it goes scanning->connecting (then I see AP address momentarily) and then back to scanning. As soon as I uncheck WPA3, it connects via WPA2 just fine.
I have used both scan/connect and manually typing in the SSID. It does see the SSID. It doesn’t matter whether I type it or scan/connect – as soon as WPA3 is in the mix it seems to fail when it starts negotiating with the EERO.
Then there are 2 options left:
Issue still confirmed in 7.11. Mikrotik still won’t connect to my Eero when WPA3 is enabled. Other devices (e.g. iPhones will connect to the Eero).
And have you created a support ticket with corresponding supout.rif ?
Nope – looks like that is my next step 