Fishing Reel

The anti-reverse latch can be a implemented via a toothed gear or an offset cam mechanism. Both are usually spring loaded and are also switched on/off by an external lever. I suspect you have either lost a small part (like the spring) or have not re-assembled the reel correctly. Try to find an exploded diagram of the reel guts assembly. Then take apart and re-assemble according to the diagram. If you did lose a part, good luck finding it or a replacement.

Sounds like the little toggle under the spool has either dropped on the floor (missing) or has turned round and is not engaging the ratchet! I take it, you've set the drag? I'm thinking along the lines of a simple fix spool reel here so if I'm wrong, whats the model number! These reels are quite basic so with a few little tweeks it should be back on your rod catching fish!