We don't want you to experience this inconvenience, @skylitedc2014.

I want you to know that helping you is our priority. This time, I'd recommend contacting the Technical Support of the online payment you're using. Someone from there can help you disable the online payment option so you can use the manual check for your vendors.

In case you need some related article in managing your vendors and transactions, you can always visit our Income and Expenses article for reference.

Let me know in the comments if you have any other questions. Always around ready to help.