If not don correctly the WPA8631P extender only pretend to be on an EasyMesh - but act as APs or at least do not copy WiFi Passwords from the router.

Resulting in dropped connections while roaming.

Manuals and Forums are incomplete iregarding important setting (and sometimes plain wrong) about setting up thsi configuraiton.

I went thorough replacement devices twice (likely unnecessarily) and spent wholes days figuring this out - so I think it's worth sharing.

This is an AI generated summary of a loooong conversation - but it's tested and correct for this configuration:

2x TL-WPA8631P v.4 with firmware KIT(EU)_V4_4.0.2 Build 20230817 (the dvice need not actually be ("KIT") but must connect via TL-PA8010P to the Router.

TL-PA8010P with firmware (EU)_V4_220507

Archer AX55 v.a with firmware (EU)_V1_1.3.3 Build 20240628

Step 1: Prepare AX55 Router

• Install latest firmware.
• Activate both 2.4 GHz and 5 GHz bands, separate SSIDs allowed but same security.
• Set Wi-Fi security mode to WPA2-PSK [AES] only (disable WPA3 for now - that is the most ciritcal part that isn't mentioned ANYWHERE!!!).
  • Note: WPA2-PSK [AES] has no significant security disadvantage if you use a long, strong password (12–15+ mixed characters).
• Enable WPS temporarily (tht is not possible with WPA3 active - hence it must be deactivated).
• Smart Connect is optional, but can be enabled later after full Mesh setup.

Step 2: Prepare Powerline Backbone

• Plug PA8010P into wall socket near AX55.
• Connect PA8010P to AX55 via Ethernet.
• Plug only one WPA8631P into a wall socket nearby (no surge protector).
• Press Pair button on PA8010P (short press).
• Within 2 minutes, press Pair button on WPA8631P.
• Wait until Powerline LED is solid.
• Repeat for second WPA8631P.
• Confirm stable Powerline network (acceptable data rates ~250 Mbps+).

Step 3: WPS-Based EasyMesh Pairing - this is essential and sometimes (falsely) even expressly discouraged elsewhere!

• On AX55, go to Advanced → EasyMesh → Add Device → Extender.
• Press WPS button on AX55.
• Within 2 minutes, press Wi-Fi button on WPA8631P.
• Wait for the WPA8631P to connect.
• If WPA8631P joins Wi-Fi but does not show under EasyMesh, proceed to Step 4 (It NEVER did for me even though is should according to official aevice).

Step 4: Manual EasyMesh Activation if Needed

• Access WPA8631P web interface via its IP address.
• Manually enable EasyMesh mode.
• Save settings.
• WPA8631P will automatically appear in AX55 EasyMesh device list as a Mesh Node.

Step 5: Verify Full Mesh

• In AX55 EasyMesh interface:
  • Confirm WPA8631P shows as Connected.
  • Confirm Wired Backhaul (if Powerline link is healthy).
• Confirm WPA8631P adopts AX55 SSID, security, password (initially).
• Test device roaming if needed.

Step 6: Optional Optimizations

• After full Mesh setup:
  • Enable Smart Connect if you want band steering and unified SSID.
  • (Optional) Switch router security back to WPA2/WPA3 Mixed for newer device support.
    • Important caution: If you switch to WPA2/WPA3 Mixed Mode, password changes must always be done by first reverting the AX55 security mode back to WPA2-PSK [AES] only, then changing the password, then switching back to WPA2/WPA3 after all nodes have synchronized. Otherwise, password updates will not propagate properly to the extenders.
  • Disable WPS again for better security after pairing is fully complete.

Important Reminders

• Always perform pairing near the AX55 for clean Wi-Fi management handshake, yes, during paring it needs to see the Wifi as if it were a wifi mesh - even for Powerline extenders!
• Powerline encryption keys are already secure after pairing; no further action needed unless you want custom keys.
• Device roaming and band steering will still work correctly even if WPA2 with WPA 3 is later activated in the router (the setting will copy to the extenders).
• Passwords wil NOT synchronize as long as WPA2/WPA3 Mixed is active (if it is later activated). But WPA3 can be decativated in the router, will then also deactivate in the extenders, and then a password can be changed and will copy to the extenders again.

Very short final summary: First build Powerline network → WPS pair Wi-Fi → enable EasyMesh manually if needed → verify EasyMesh + Wired Backhaul → optimize Wi-Fi settings if desired.