A warm welcome and thank you for joining us here in the Community, @Marino2. Be assured, we will do everything to get this matter cleared up as soon as possible.
You'll want to check around the Banking menu, things like being unable to find the transaction may be stuck somewhere around the Banking menu. Here's how:
Go to Bookkeeping, then Transactions, then choose Banktransactions (Take me there).
Select the tile for the bank or credit card account you downloaded the transaction.
There are three areas you may check:
Start in the For review tab. Usually, it's where QuickBooks puts recently downloaded transactions. If you find the missing transaction, categorize it into an account. Transactions don't show up on your books until you categorize them.
Next, check the Categorized tab. This tells you what happens to transactions you already categorized. Specifically, review the Added or Matched column. This tells you which account you categorized the transaction into. If you find your missing transaction, but it's in the wrong account, follow these steps to unmatch and move it.
Also, about your transactions from 5 months and still unable to download them, I suggest reaching out to your bank to check if there is maintenance. You may be able to talk with one of their experts who may provide you with useful information.
You may visit these links to guide you on how to categorize your transactions and reconcile your account flawlessly: