It's my priority to ensure that you'll be able to link your bank account in QuickBooks Self-Employed successfully.
To start with, I want to ask what financial institution are you working with? Any further details are much appreciated so I can narrow down this matter.
If your bank has been connected already and transactions are not downloading, you can run a bank update. Just click the Refresh All button to run the update.
If the same thing happens, you may consider uploading your bank transactions to your account manually.
Let me guide you how:
Sign in to your bank website and follow the instructions on how to download your transactions as a CSV file.
Once downloaded, navigate to the Gear icon in your QBSE account.
Select Imports.
Click Import older transactions for the account you want to add the transactions to.
Select Browse and locate the downloaded CSV file, then click Open.
Review the column headers and data then click Continue to start the import.