There will be something lying across the filter (money? lollipop stick,cotton wool bud etc) so it is effectively jammed.
You will need to remove the pump.
Its pretty straightforward.
Remove lower kick plate -one screw near the front next to the filter and the
panel slides to the left and pulls away.
There is one screw at the top (torx btw) just above the filter and the pump lips in to the metal plate.
Tilt the machine say 45 degrees back against the worktop and you will be able to access from underneath.
You need to then ( eg with vice grips ) remove both the inlet and outlet hoses and remove the pump and housing from the machine.
Some of the Bosch have an extra drain hose at the front which you may want to use to drain the water from the system prior to the above -otherwise sponges and towels handy.
If you get this far then you will probably be able to the fish whatever it out of the filter that is preventing its release.
If its a load of money then I can send you my address
Happy Xmas!