Here's my experience
Does your cassette adapter have gears inside that cause both spindles to turn? By this I mean that some adapters have two empty holes in them while some have gears in them that are connected. You see, some cassette players work fine with adapters that have two empty holes because the cassette player doesn't mind if only one spindle turns. However, some cassette players require both spindles to turn and if there are no gears inside your adapter, then the player will turn one spindle, realize that the other spindle is not being turned, and eject the adapter. I have a Sony Tape player and a Sony cassette adapter, but I'm annoyed because this model Sony cassette deck will not accept my adapter because it doesn't have gears in it and only one spindle turns. So, I had to buy a Monster cassette adapter that has gears in it and it now works fine. Does that make sense to you? I hope so.