how do I fix Aqualiser Digital shower?

Try this site:

https://www.showerdoc.com/shower-spares/aqualisa

Select your exact model and you should find some FAQs and the opportunity to ask a question of your own

You could be a lot more specific about "some sort of code". Set down exactly what the shower is telling you when you post on showerdoc

Fyuigfdd
April 2018