I'm having this exact issue right now. The difference is, I have tried every single cable I can find in my apartment. They still work when used to connect my phone, I can even browse files then. But all of them either don't get any acknowledgement from my PC or say it's not recognized, when hooked to my Switch.
I know my Switch is in RCM mode because I briefly got confirmation of that the first time, it said it recognized an RCM device but the driver wasn't installed (even though I have used the program before so idk what that was about). I installed the driver and then tried to send the payload, but the program hung. I killed it and tried again. After that it just stopped noticing my Switch entirely and has been that way since, with all cords. From everything I've read online I'm led to believe I somehow fried the USB-C port on my Switch. I really REALLY hope that isn't the case. But idk what else it could be, I refuse to believe ALL my cords suddenly stopped working at the same time, specifically just for a Switch, while remaining entirely functional for transferring files to and from my phone.