I have been getting this error above for the last day and cannot figure out why the system is not picking up my account numbers. I have picked through many of the topics already on this forum and tried every suggestion I can see to configure this. Please see screenshots below of the configuration. The invoice is for 1 "Television" with item number 454545.
Item 454545 belongs to "DP Items" Item Group:

DP Items group has had Posting rules configured for the group:



I even ensured that the account numbers were in the "Accounting Structure" setup:

But the ledger account is still blank in the Subledger Journal and Accounting Distribution screens:


And of course, this error occurs when attempting to post:

Can someone please help me out to find the setup missing? I am unable to continue with my work until I can get an invoice successfully posted in the system. Please note, I am a developer and so I have very little knowledge of the ERP and accounting. So if there are setup tasks I forgot, please provide menu paths to the process and what the data should look like. Thank you very much for any assistance you can provide.