Hi @bartyu
Here's the [document|40385|tech sheet] that will help.
Run the ''Service Diagnostics with Error Codes'' as shown on p.2 (left side at top of p.2) and check what error codes are being displayed.
The error codes and their possible causes are also shown on p.2.
If you find the problem and it is a faulty part that needs replacing, here's the [https://www.searspartsdirect.com/model/3zc0isnx15-001198/whirlpool-wdf750saym0-dishwasher-parts|parts list] that will help.
Locate the wanted part in the list and note the ''manufacturer's part number'' for the part that is listed with it. Search online for the ''part number only'' to find suppliers that suit you best.