summery account for vendor account vend/00001 in posting profile GEN does not exist.
I have moved this from known issues forum as it is an end user issue.
Go to the general posting profile and define the ledger account for creditors. You have not told it where to post the liability in the ledger so it stops you.
1st of all, create one account in the chart of accounts form for Summary accounts in GL module. Now, Create Posting profile in AP module.(AP>Setup>Posting profiles).
In posting profiles form > setup (tab) mention account code as you required. (Ex: Table/ Group/ All) and assign summary account.