When I put down a belt observer near a conveyor belt, and put an item into its filter and put it into any mode, it doesn't do anything when the item that I put into its filter passes it on the conveyor belt.

Was the belt rotating and items passing by?

Yes the belt was rotating and items passed by

Were they the same items as the one on the filter?

Yes they were

I've put together a quick video of the observer working in the last version (b) properly. If you are seeing different results a quick video like this would probably help the developers https://drive.google.com/open?id=1T9bbc4Syey19MyqacUWV0GQoGIgBfqgV

Here is my video that I recorded of the belt observer not doing anything no matter what I did. Here is the video:
https://drive.google.com/file/d/1OQzmNjyHsF_wocCf7fCzyomgV-X74k6K/view

I also tried the belt observers on the version before version (b), version (a), and they didn't work on that version either.

You have a shaft under the belt where the observer is placed. Dunno if it is intended, but that combination does not work as the observer adds it's own "structure" under the belt.

This is not a bug, this is just me not realizing that you have to have a gap in the conveyor belt in order for the belt observer to work. I didn't even know that you don't have to have shafts on every block to form a belt.

Thanks

I think we found the reason at the exact same time. No problem, I didn't know that it didn't work with a shaft so we both learned something :)

Yep