Thanks for sharing to the exact error message, Pfarhadieh.
You can resolve the issue by deactivating online banking first and then merging the accounts.
Before performing the following processes, make sure there are no active statements in the Online Bank Feeds. If there are downloaded transactions that have not been matched, you’ll have to do that manually.
Once done, you can now deactivate the account. Let me walk you through the steps.
Next, open the accounts and merge them again. For further guidance, check out the Merge Accounts, Customers, and Vendors article.
Let me know if you run into any hurdles while following these steps. I’ll be right here to assist further.