Hi Vladislav
As you said delivery is created in ECC and cannot found in EWM.
check SM01 and SM02 in ECC and then same in EWM.
if your queue is stuck in SMQ1 in ECC then its issue of distribution model or some other integration part of ECC - EWM .
Then Check SMq1 and SMq2 in EWM. If you found any queue stuck try to reprocess and check SLG1 for error log to get correct issue of why you can not see IDN in EWM.
try to flow new sto for check. Don't reprocess the old one. so that in between if you have changed any customization which will may resolved issue.
Regards
Suraj