Expense Report Not Submitted but Reverting Back to Pending Status

Hello -

I wanted to ask about an issue that we are encountering. The issue is occurring whenever we submit an expense report and upon clicking the refresh button, it goes back from Submission in Process to Pending status.  We checked IB and entries are going to DONE status as well as SMTP is working correctly.  All configurations were applied (Transaction Configuration, Transactions Registry and Approval Process Setup). After expense report is processed in IB, we are receiving an email notification (sent to Admin) that Expense Report cannot be approved due system error.

We are also getting the following error in the PS_EX_SUM_APPR_ERR record.