Most likely water has leaked into the bottom of the unit. There is a float and switch in there which detect water pooling in the bottom pan. When tripped, it produces the F2 error and constant running drain pump, like you describe.
You could try just pulling the unit out and tipping it to drain the water (onto towels or whatever)... This might be a quick way to verify the issue, but it probably won't solve the basic problem of why it leaked.
A better way would be to open the bottom of the unit (from either the back or the front, T15 driver required), and drain/absorb/vacuum the water out. Make sure everything is dry before starting it again. Then figure out why it leaked in the first place. It could be a clogged drain, debris in the drain pump, or some other leak. Ideally you can run the washer while watching under it for leaks.
I found this PDF helpful for disassembly and testing instructions:
https://applianceassistant.com/ServiceManuals/asko_dishwasher_3000_5000_series_service_training_manual.pdf
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