I appreciate you trying some steps to get this issue sorted out, starnroanise.

An interrupted connection between QuickBooks and your bank is usually causing this issue. Since you’re still unable to get these transactions, I’d recommend uploading them manually through CSV. This involves logging in to your bank, downloading the transactions from there and saving it in your desktop. 

For the detailed steps, please check this out: Manually upload transactions into QuickBooks Online.

It would be best as well if you’ll provide us your bank name so we can check if there’s an ongoing issue. Stay around if you need anything else.