Can you find out what it would cost for someone to come and check it out and see whether it is worth fixing? If it's a computer problem then it's hardly worth it but 3 to 4 years is not a good life cycle so I would want to check it out.

My last dishwasher just replaced lasted 8 or 9 years.

If it heats it's own water, perhaps the heating element has gone?  I bought a Dishlex earlier this year, very happy with it

I would give Bosch a ring and explain what has happened and see what they say. It may be simple or it may be cheaper to buy a new one.

My first thoughts were, filters blocked, thermostat has moved or not working and as said heating element which could just be a fuse.

Have you had any power surges or circuit breakers tripping lately?

As horizon says call Bosch, it may be common problem that they can estimate a repair immediately.

Certain models were reknown for not heating the water. The problem was something to do with the control/circuit board thingy.

Or it could be the heating element is buggered. Usually if the machine is not heating the water, the wash cycle time will take for ever.