I had this issue and worked my way through it.
Following the advice of one of the above posts I disconnected my mac from its external monitor and opened Spine on the laptop screen. It worked.
When I plugged my USB-C connection back in, I was prompted to "OK" the connection of the new devices. I'm guessing that was relevant because Spine now opens on the external monitor.
More details:
My situation is an M2 MacBook air that had just been updated to MacOS Sonoma (14.3.1) for the first time. Sonoma was released about 5 months ago, so it's not a new OS at this point.
I did the update on Friday and ran several other apps all weekend without ever being prompted to approve the connection to the external devices. I even gave it a good restart after the update for no particular reason. It wasn't until Monday morning when I tried launching Spine that all of the above occurred.