I ran updates yesterday and noticed an update for GUFW was included.
Today, I checked my firewall's status, and it wasn't active.
Now...I'm almost positive that I had turned on my firewall...I can't imagine that I wouldn't have. So, I assume the update to GUFW turned it off?
All of that to say this...if you receive an update for GUFW, check your firewall's status afterwards...and you may want to check it after rebooting too.
Again...this could have been an oversight of mine, but it's better to be safe just in case.
EDITED TO ADD: It was apparently my oversight. I apparently hadn't turned it on. Don't know how that happened!