I have used one USB relay in the past it was not reliable at all. It stops working after two or three weeks and I had to replace it. The replaced one also stopped working now. From the reviews of other USB relays from amazon, this is a similar issue with all of the USB relays.

The product I used was: www.amazon.ae/KNACRO-1-Channel-5V-Relay-Module/dp/B0797PDXVV/ref=sr_1_11?crid=2AMVAZQJ0N5HN&keywords=usb+relay&qid=1706184283&sprefix=usb+relay%2Caps%2C208&sr=8-11
Now this is out of stock

 

This request does not provide enough information, neither about the application nor about the failure. And I do not chase links very often.
So the TS needs to supply more information about the application and the failure, as well as a bit more about the product. "Relay" covers a very broad realm in my world, so more specific description, please.

 

some vehicles are also unreliable and fail prematurely. must be vehicles fault...

 

#3 is a bit off topic.
What is the "USB relay" supposed to be doing?? I am guessing that it is supposed to serve as a remote on/off switch controlled from a computer, connected by a USB cable. But it might be something different from that. AND we have no hint as to what failed to happen.

 

Does the unit fail if operated with rated load... or no load? If so then it really is unreliable. But i have a hunch that is not the case.

What is the load? What type? Relay is only rated for 10A and that is when conditions are ideal (resistive load at 120VAC). For other types of load, and for different load voltage, relay must be derated (see 7A even for restive loads). It also must be derated for DC use. That is what datasheets are for and this one tells that if load is inductive and circuit is DC, maximum current may not be 10A, it may be only 3A... and that is for stated load type. For others it could be different and - possibly even less than 3A! So without knowing what the load is, there can be no suggestions how to address the issue. in general, overload is likely to blame. in that case, USB relay like this may be used to drive another relay that does have correct contact rating for the load.



The next part is suppression... What kind of suppression is used? if none, contacts will errode way too early even if circuit and current are within specs.

And what about the usb port? Did you try different one? If using hub or cable, did you try direct connection? are you sure that there is no busted USB port or cable or that voltage at the module is 5V?

if it is the relay that fails, typical modes of failure are that contacts burn up or get stuck (relay overheating, causing plastic to melt) or contacts weld (also causing it to get stuck).