Hi Evhen,
I have also come across this error in PSCD once.
There could only be three major issue scenarios where it can happen.
1. If you are using the GL account for receivables/payable (i.e., you have maintained this in posting area P000), the field 'reconciliation account for account type' is not set with "V". It must be set with "V".
2. If you are using the GL account for benefit/expense (i.e., you have maintained this in posting area P001), the field 'reconciliation account for acocunt type' is not set with blank. It must be blank.
3. The GL account is blocked for posting.
Please check these first.
Alternatively, you can check in the FM FKK_HKONT_CHECK as for which condition the IF block is getting satisfied, that will shed more light for your investigation.
Hope it helps, let us know how you go.
Thanks
Bodhisattwa