There are several steps required to set the microphone you want to use for an Audio Track in Studio One on the Mac.
It's more stuff than one might imagine or desire.
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NOTE: These are the configuration steps when using the Built-In Microphone. If you are using a separate, standalone microphone, then the steps will be a bit different--but conceptually the same--where you need to let macOS and Studio One know you are using a separate, standalone microphone and its interface (USB, Bluetooth, external digital audio and MIDI interface, or however you connect it to your Mac.]
Make it look like these screen captures, where you begin by telling macOS in STEP 0 what you want to do using Audio MIDI Setup and specifying the Built-In Microphone and Built-In Output. Then do STEPS 1 to 3 in Studio One.
Perhaps this will help, at least if you are using the Built-In Microphone of your Mac. If it doesn't work, then perhaps I can create a set of screens for configuring a B.L.U.E. Snowball USB microphone, but not on any other way to connect.
I don't have a Bluetooth microphone, and using a MOTU 828mk3 Hybrid and a standard XLR microphone is not so practical at the moment. I could do it, but it requires cables and doing a bunch of stuff, plus the practical aspect is that it's basically the same as using the Built-In Microphone of your Mac. Doing it with the MOTU 828mk3 Hybrid and an XLR microphone conceptually is the same; but it requires a bit more configuring and another step or two.
Not much else comes to mind, although there a few guesses, (a) MacBook battery is low (unlikely and a wild guess), (b) standalone microphone battery is low, (c) standalone microphone is intermittent (broken), (d) microphone cable is intermittent (broken).
Let us know if this solves the problem . . .
P. S. Among other things, I write books on digital music production; so I practice and improve my skills by touch-typing and doing screen captures every day, where I edit the screen captures (a) in Graphic for Mac, which is my primary graphic editor, and (b) in Krita, which is my secondary editor for more advanced graphic editing and painting. For reference, this post took about 3 hours; so it's like golf. If you want to be good at playing golf, then you need to play golf every day for more than a few minutes, which is the same with instruments and singing.