Model : TL-WPA4220KIT + 2x TL-PA4020P

hi,

i've got four devices.

they are working great, as long as there are only any two paired to each other.

now how do i connect them all together? when there are two paired to each other, as soon as i want to pair the third one, the other one loses connection to the first one.

according to https://www.tp-link.com/de/faq-1250.html it should be possible to pair at least SIX adapters?

i tried this https://www.tp-link.com/us/faq-319.html - step 1 and 2 work ok, but after repeating step 2 for adapter B, adapter C loses connection to adapter A ?
(but adapter B is then connected to adapter C)

so, how should one pair another one to two existing devices? or am i misunderstanding something?

thanks in advance,
chris