TP-Link's connection article splits the checks between the Deco and the device. On the Deco: confirm the wifi name and password under More, Wi-Fi Settings; check the block list; turn off Fast Roaming under More, Advanced, Fast Roaming, since some devices cannot join when it is on; temporarily turn off the 5 GHz network, because smart home devices that only support 2.4 GHz may fail to join if the 5 GHz network is active during setup;
The checks in more detail
try the guest network as a test; change the wireless security type under More, Wi-Fi Settings, Security; and remove special characters such as apostrophes from the network name and password. On the device: make sure it is not using a static IP, check the signal strength, power cycle both device and Deco, update the wireless adapter driver on a computer, and contact the device maker if it still fails.
Wired devices connect to the Ethernet ports on each Deco, and the M3W has no Ethernet port. If the app cannot find a Deco during setup, TP-Link also has a separate article for when the Deco app says it could not find a Deco. When a single device is the only failure, borrow another device with the same wifi standard and try the same room. If the second device joins, the first is the problem, and its maker's support or a driver update is the answer rather than more changes on the Deco. If a device joins but shows no internet, that is a different fault from not joining at all, and points to addressing or the WAN, so check other devices and the Deco light before touching the device.
Differential
Likely causes of “TP-Link Deco mesh wifi will not connect one device”, and how to tell them apart
- 1
Fast Roaming
What separates it Some devices will not join because Fast Roaming is switched on and they do not support it
How to confirm Turn Fast Roaming off in the Deco app, and try to join the device again
- 2
5 GHz active during setup
What separates it A 2.4 GHz only gadget fails to join because the 5 GHz band is active during its setup
How to confirm Turn the 5 GHz band off for a moment, and set the gadget up on 2.4 GHz
- 3
Special characters in the name or password
What separates it The join fails because the wifi name or the password has special characters in it
How to confirm Remove the special characters, such as apostrophes, from the name and the password
- 4
A block list entry
What separates it The device is refused because it is on the block list in the Deco app
How to confirm Remove the device from the block list, and then try to join again
- 5
A static IP on the device
What separates it The device gets no connection because it uses a static IP address
How to confirm Set the device to use automatic addressing, so that the Deco can give it an address
Before you touch a setting
Record this first — changing settings destroys the evidence
- The device and the exact error
- Which wifi band the device supports
- Whether other devices can join the same network
- Whether it is on the block list
Try in this order
0 of 7 completedCheck name and password
ReversibleCheck the name and the password in the app, under More and then Wi-Fi Settings.
Check the block list
ReversibleCheck the block list in the app, and remove the device from it if it is listed.
Turn off Fast Roaming
ReversibleTurn off Fast Roaming under More and then Advanced, since some devices cannot handle it.
Turn off 5 GHz briefly
ReversibleTurn off the 5 GHz band briefly, so that 2.4 GHz gadgets can complete their setup.
Try the guest network
ReversibleTry the guest network as a test, to see whether the device joins there, and then test again to see whether it helped.
Check the device
ReversibleCheck the device itself, meaning its static IP setting, its driver and its signal strength.
Power cycle both
ReversiblePower cycle both the device and the Deco, waiting for each to start up completely.
Model-specific
What is true of this model and not of its siblings
- Bands
- The BE85, BE63 and XE75 add 6 GHz, which older devices cannot join.
- M3W
- The M3W extender has no Ethernet port.
- Other models this page answers
- These steps also fit the Deco BE63 mesh, Deco XE75 mesh, Deco X55 mesh, Deco M5 mesh.
Stop boundary
When this stops being a self-service repair
- !If the device joins the guest network but not the main one, contact TP-Link support
- !If only that device fails everywhere, contact its maker
- !If the Deco cannot be found in the app, reset it and set up again
Evidence ledger
Sources behind this answer
Deco-side and device-side checks.
Finding the Deco in the app.
Main, satellite, client and random reboot fixes.
Every LED color and pattern by model.
The company and its products.
Exact questions
Common questions
Why will my smart plug not join?+
It may be 2.4 GHz only; turn 5 GHz off during setup.
What is Fast Roaming?+
A feature some devices are not compatible with.
Can special characters break the connection?+
Yes, special characters such as apostrophes in the name or password can stop a device joining.
How do I check the block list?+
You check the block list in the Deco app, and remove the device if it is listed.
Does the M3W have Ethernet?+
No, the M3W does not have an Ethernet port, so it cannot be wired to the network.
Can I use the guest network as a test?+
Yes, you can use the guest network as a test, to see whether the device joins there.
What if the app cannot find the Deco?+
Use TP-Link's article about finding the Deco, which explains what to check if the app fails.
Do drivers matter?+
Yes, update the wireless adapter driver on the device, since old drivers can stop it joining.
Should I use a static IP?+
Not on the device for a Deco network.