Problem "The Telnet open command is invalid" when adding gateway 3 (custom 1.5.4_0090)

[Slovator]

Home Assistant: 2023.2.5
Gateway 3 firmware: custom 1.5.4_0090
Telnet: opened (admin/admin) but in "MiCloud Device Information" after adding integration using login and password to download tokens and names for devices from the cloud, "Telnet: wrong_telnet" is displayed.
Integration version: v3.3.5
HomeAssistant and Gateway 3 are on the same subnet.
Fixed IP-address for Gateway on Router
Wi-Fi Router settings for 2.4GHz:

• Fixed channel: 10
• Channel width: 20MHz
• Authentication: WPA2

When I try to add a gateway with a token, I get the error: "The Telnet open command is invalid" (I leave the "key" field blank).

[TheRedIvan]

Same here!

[AlexxIT]

Collect debug logs

[maddoglee]

Same here.. I just bought a new gateway and it has 1.4.6_0040 and I cannot add the device. It needs a key, but I cannot seem to obtain the key anywhere.

[AlexxIT]

You don't need key for 1.4.6

[maddoglee]

That's what I had thought, but I am getting this error when trying to add my new gateway (ZNDMWG02LM):

I've tried telnetting with admin/not password, admin/admin, admin/password, admin/123123. Nothing seems to work. It's brand new and I haven't updated the firmware yet.
Thanks for your super quick response btw

[maddoglee]

I resolved this by upgrading from 1.4.6_0046 to 1.4.7_00160 through the Mi Home app. It seems that telnet is blocked with an unknown password from the factory. After upgrading to 1.4.7_00160, everything worked with no entry in the "key" field.
The Mi Home app is now giving me the option to update to 1.5.6_0001. there is definitely no issue with Xiaomi Gateway 3.
For the others here, you have to figure out how you can get telnet working first.