Hi,
Please check
1. Whether PO contains any G;L if yes that is created.
2. Whether all the G/Ls pertaining tax code have been created.
3. Whether any alternative reconciliation account is mentioned in G/L master of Vendor reconciliation account and that have been created.
4. If all the G/Ls created then check the same in S_ALR_87012326 - GL Reports (Master Data) for your COA.
Hope, this solves your issue else revert.
Regards,
Tejas