@Solla-topee attached a tcpdump capture file of what happens when I try to initiate firmware update using Tapo app from two affected P100 plugs. you can open it in wireshark. and a few screenshots.

I've already tried all workarounds I could think of, including taking the plugs to work and connecting them to two different wireless APs there. I've also tried using my mobile internet, so its 4 ISPs total. the logs show they are not blocked on the network level though so changing ISPs are not going to do much.

MAC addresses of affected plugs should be in the capture file. tell me if I need to provide anything else.

@Solla-topee one more capture file attached.

my home router is a keenetic, at work we're using a bunch of different bridged APs and juniper srx units. no outbound network filtering anywhere.

edit - just in case, only some plugs refuse to update. i have a few others HW 1.00 which update just fine on my home network. so it seems to be specific to HW 1.20 plugs.

I'll post an update here: I've been contacted by a TP-Link engineer, who provided me with a way to collect debug logs related to the situation. I've tried doing the process as he described, and then - for whatever reason - I managed to update one plug. Then I want to normal Tapo app and - lo and behold - the rest of the affected plugs also updated just fine.

I'm still not sure what's the root cause here, but this situation is resolved for me. There were no network/router/SSID/whatever changes on my end, something just got unstuck, I guess.

Thanks to everyone for help.

  @Solla-topee 

Har hatt samme problem med p100, som var plassert i dårlig Wi-Fi-dekning. Flyttet pluggene til et område. Med god Wi-Fi. Tilbakestill pluggene og installer på nytt. Løste problemet

  @Solla-topee 

Buonasera, ho due TAPO P100 V1.20, una delle due non si vuole aggiornare in nessun modo alla versione1.4.10 Build 20211104 Rel. 35882

Good evening, I have two TAPO P100 V1.20, one of them doesn't want to update in any way to version 1.4.10 Build 20211104 Rel. 35882

MAC 84-D8-1B-DB-8E-69

1.4.9 BUILD 20210621 REL. 30941

Suggestion?