Hi ReaderMac,
Thanks for using Apple Support Communities! I see you're having trouble connecting a Bluetooth speaker to your MacBook Pro, and I'd like to do what I can to help out.
Have you restarted your Mac since noticing this issue? If not, go ahead and do that, as a restart can resolve unusual issues.
Log out, sleep, restart, or shut down your Mac
Make sure that your speaker is discoverable, so that your Mac can find it.
Even though this article doesn't specifically say speakers, it still applies: Using a Bluetooth mouse, keyboard, or trackpad with your Mac
I was able to find this article on the Bose website: Pairing and connecting to a Mac® computer which shows it applies to the SoundLink wireless Mobile Speaker.
Check with the speaker manufacturer for any additional help. Let them know which macOS version you're using, and what steps you've tried already.
Take care!