"Not changing anything" doesn't tell us anything. What settings do you actually have?
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My standard answer to "it used to work and now suddenly it doesn't" is to NOT USE DEFAULT!!!!!!!!! Always choose a specific device, *in OBS*. The reason is that Default defers the choice to the operating system, which can and will change it on you. So then you're connected to a different device, which is a fairly major change without YOU having changed anything.
Never use Default. Always specify the actual device *in OBS*.
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Now, you say that OBS's meter still moves. That hints at a different problem. So again, "no change" means nothing. What do you actually have?