Hi Andrew
Have you checked, that your bank account allows checks as payment method? Also the balances and the limits are considered. If this is as required, you can actively configure the sequence the bank accounts should be used.
Please go to Business Configuration -> Activity List -> Fine Tuning and search for "Global Settings for Payment" (hint: this option might be optional in your system).
Here you see "Prioritize Bank Accounts and Payment Method based on Amount". This can help you to put your standard bank on priority one for checks.
Hope this helps.
Best regards
Marlene
ByDesign Platinum Engineering