Thanks for making us aware of your situation, katherinecrouch6.
I'll give a brief overview of what might have happened.
When a bank stops updating new transactions, it might be because of some maintenance updates from the bank's end. What you can do to get those transactions updated again is to refresh the connection by going to the Gear > Bank accounts > Refresh all.
If you've deleted the account by clicking the trash icon, it will delete all of the related transactions. This is why you only see some of the recent transactions after reconnecting the account.
To get all of the transactions added back in the Transactions page, you have the option to add them manually. Here's an article for the step by step instructions: Add older transactions to QuickBooks Self-Employed.
I'll also add these articles to learn more about deleting and connecting a bank account in QuickBooks Self-Employed:
For any follow-up questions or other concerns with your QuickBooks Self-Employed account, please let me know in your reply. I'd be happy to help you out again. Take care!