Without the information requested in my previous response, I can only give you a general answer however, I hope this helps.
E15 in your dishwasher indicates, water has leaked in the base of appliance and activated the anti-flood device.
You will have to unplug the appliance and pull it out, then tip it backwards by around 45 degrees so excess water drains off completely.
After you have done this, check the drain hose where it connects to house drain and make sure it is not clogged.
Then please clean the mesh filter from inside and make sure it is not blocked.
Now, reconnect everything and plug it back; select any program.
It should work however, if the problem occurs again you will have to replace the flow sensor and/or aquastop valve to solve the issue.
Siemens provides 2 year warranty hence, it is out of warranty.
Alternatively, you may call Siemens at 03448 928 999 to book repair.
If there is anything else I can help you with, please let me know.