Thanks for joining the Community. Are you viewing your account on the mobile app or web, and have you tried viewing the invoices in more than one web browser like Google Chrome and Microsoft Edge? Please also double-check that you're signing into the correct account.
If you've set up more than one QuickBooks Online account, you can switch to the other company by following the steps from this article: Switch between company files.
In addition, if you're still not seeing the invoices, I recommend checking the Audit log. Another user may have deleted the invoices, and this is where you can see the account activity log. Here's how:
Click the Gear icon, then select Audit Log.
Adjust the filters to the appropriate User, Date, or Events to narrow the results.
Then, you can verify if a user deleted the invoices. If deleted, you need to recreate them.