Kobelco SK295-9 derate issue (code w015) after def/adblue injector replacement. What should I check next?

[IamBruce_Driver]

We've already replaced the injector with a new OEM/Bosch unit, but the machine is still in derate and showing code w015. We also confirmed that def is reaching the injector. At this point, we're not sure what to check next.