There are times that your browser is full of frequently-accessed page resources, causing QuickBooks Self-Employed (QBSE) to act weirdly. You can log in to your QBSE account using a private browser. This is to rule out any problems related to your browser.
To use a private browser, here's how:
Google Chrome: Ctrl + Shift + N
Internet Explorer: Ctrl + Shift + P
Mozilla Firefox: Ctrl + Shift + P
Safari: Command + Option + P
Once done, you can go back to the Bank Accounts page and click Refresh All. Wait for a couple of minutes for the update to complete.
If new transactions are already downloaded, go back to the browser that you're previously using and delete your browsing history. This is to clear out all the internet files or cached that're possibly causing the issue.
Here are some articles that can help you get going: