Question Bluetooth can see smartphone and laptop, but not keyboard?

[rgdraconic]

I'm currently using this adapter on my desktop:

https://www.amazon.com/gp/product/B01N5MGEUS

Which has no problem seeing my Samsung S9+ phone or a Lenovo laptop in discover mode behind me, however, I am trying to get it to see this keyboard:

https://www.amazon.com/gp/product/B06ZY9T2ZN

Which both the smartphone and laptop can see just fine, pair with just fine, but the desktop cannot.

Any ideas? I've tried all manner of CSR drivers, all manner of Asus BT400 drivers, left it as Generic Bluetooth Radio - I'm completely stumped.

Thank you for helping out a newcomer!

 

[rgdraconic]

I should mention I've tried two other BT adapters - and the keyboard doesn't seem to show up using any of them.