Can't select bluetooth speaker for output

Not much information to work with.  But, in general, go to Windows settings=>  Bluetooth & devices=>  Devices, see if the bluetooth speaker shows as connected under Audio group.

After confirming that the speaker is connected, click on the volume icon in tray area (bottom right corner of your screen).  Click on the far right of volume glider will allow you to select a sound output device, click on the bluetooth speaker in the list and the speaker should play.  Making proper volume adjustments for optimal playback audio.

@Chino de Oro​ Laptop is Dell Inspiron 7591 2n1, blue tooth speaker is soundcore Motion X600 BLE. My laptop connects and pairs, but doesn't show as audio device on Windows 10 settings. Phones can connect to the bluetooth speaker.

@Chino de Oro​ - I just determined that the laptop works with another bluetooth speaker, so there must be some setting (registry?) needed to enable soundcore Motion X600 BLE as an audio device.

I chatted with support for 20 minutes, and support ended up falsely claiming Dell Inspiron 7591 2n1 doesn't support bluetooth, and needed an optional or third party bluetooth card to work.

for some reason some speakers work better with Apple than a PC

Glad that I could help.  Once you confirmed that the speaker is connected, it would work without problem.