Yes - checking that desired 7.1 sound is indeed as it should be is important.
It is all too easy sometimes to change a setting and then forget to "Save", "Apply", or otherwise verify the change.
However, Windows itself, the audio hardware and its drivers, plus application software (music players, music editors, games) generally include and involve multiple settings that the end user (you) can change.
So all of those options must be looked at (doublechecked) to verify that they are set at the necessary or required value or selection.
The speaker icon is a starting point. You can also get to many of the same settings via "WIN" + "I " > Devices.
Some selections may restrict or force other selections. A mismatch may change to a default value.
What I suspect is happening is that when you make an instant edit the audio choice (7.1) is disabled for some reason. Perhaps the editing software does not directly support 7.1 editing and "chooses" 1.7 for you.
And does not or otherwise is not able to put things back to 7.1 audio or to any audio at all.
Read through the editing/instant replay software documentation. Could be some notes or other fine print that, when carefully read, will provide an answer.
They will not necessarily or directly say that "7.1" (for example) is not supported but the documents may have wording that, without careful attention, could make you believe/assume/expect that 7.1 is supported.