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September 14th, 2025 18:14
P3421W, KVM, hub stopped working
For four years, I've been using the monitor with a desktop and laptop (both Ubuntu Linux). I use a USB hub to connect a speaker, camera, keyboard, mouse, and wireless headphones on occasion. It has worked flawlessly. This morning I went to use the desktop, and nothing attached to USB worked. I tried to change inputs to the laptop, and nothing attached to USB worked. I can attach the hub I've been using directly to the desktop, and it works as expected. I can attach the hub to the laptop, and it works as expected. The laptop is attached to the monitor via USBC. The desktop uses HDMI and USB-B. The monitor still shows video fine for both inputs, it just seems USB is no longer working. I powered it off for a few hours, and it didn't fix anything.
DELL-ChrisM2
Community Manager
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156 Posts
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September 14th, 2025 19:39
Check the P3421W purchased warranty status by going HERE and inserting the private Service Tag.
I can attach the hub
* What specific hub model?
Assuming that you tested the hub in all four USB-A downstream ports?
(8) Two black USB 2.0 downstream ports
(9) Two blue USB 3.2 downstream ports
* Turn the P3421W off
* Disconnect every cable (yes Power cable) and device from the P3421W
* Press and hold in the rear P3421W power button for 8 seconds
* Reconnect all cabling and devices to the P3421W and retest
AUGrad98
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September 14th, 2025 20:17
Thanks! Since everything was pretty much unhooked already, I removed the power as well, pressed and held the button, and plugged everything back in. It didn't seem to make a difference right away, but after opening my laptop to force a signal, it started working like it should. It still didn't work with the desktop, but I moved the USB cable from the monitor to the desktop to another port on the desktop, and it started working too. So, things seem to be back to normal now.
Just to answer your questions, though, none of the USB ports on the monitor were working. The hub is a SABRENT 4-Port USB 3.0 Hub with Individual LED Power Switches.
(edited)