I have (3) total Trezor Model-T hardware devices. I have a USB Hub and have all three plugged into one Windows 10 Pro PC. Connecting the first two trezor model-T’s and going through PIN Code authorization … the first two Model-T’s connect properly and I can see them available ready to work in the Trezor APP. However the third Trezor Model-T device only shows in red color (on the device) “NO USB CONNECTION”. Please advise: How many total concurrent Trezor Model-T devices can be concurrenlty plugged into one PC all workable at the same time?
If the limit is TWO Model-T’s --then I’ll buy 2 other brand devices so I can achieve my desired working setup.
Thank you for any info about this question/problem?
Hi @mundee,
As a general rule, if you connect your Trezor device(s) to an USB HUB then the HUB should be powered to ensure that the devices receive enough power. Also, check that the USB cable(s) you use are fit to transfer data and not only charging cables.
I don’t know how many Trezors you can connect at the same time, or if there’s a limit. Only SatoshiLabs can answer that, I guess. Developer @matejcik perhaps.
I have two Trezor Model T’s myself but have never connected them at the same time, to avoid confusing myself about what device I’m working with at any given time, but I guess it can be done – as you have proven. 
There is no Trezor-specific limit. You can have 57 Trezors at the same time, if your PC can handle it.
The most likely issue here is with your USB hub. Trezor T with the regular (not bitcoin-only) firmware behaves as two USB devices at the same time: a Trezor interface and a FIDO/U2F interface. It is kind of weird, but technically possible, that your USB hub would, e.g., have a counter for 4 devices, and will not let the last Trezor connect because there’s already “too many devices”.
You can easily verify this by plugging the last Trezor into your PC directly, bypassing the hub. It should work fine.