Thanks for the replies. I tried adding 'pi' to the gpio group.
It said it was already a memory of the gpio group.
I tried the rpi_ws281x repo on github, and ran it w/o sudo on pin 10 (the SPI pin)
but no response from the LED. I connected the LED string to pin 24 on the 3B+ header.
Edited the strandtest.py to make sure I was using pin 10. still No luck.
Next I changed the python script to use GPIO 18 (for the PWM). Moved to pin 12 on the 3B+ header,
and ran the python script as sudo. It worked!
So either I need to crack the code on using the SPI pin, or get octoprint running as root. I realize this is a security issue, but my printer is behind a firewall, and has smoke detectors on it...
Any suggestions are greatly appreciated.