Let's carry out some simple troubleshooting steps so you can access your customers. Please allow me to help you how to retrieve your customer list. The completion of this task will only take a few minutes.
We try logging in using an incognito or private browser. Refer to these shortcuts below:
Google Chrome: press Ctrl + Shift + N
Mozilla Firefox and Microsoft Edge: press Ctrl + Shift + P
Safari: press Command + Shift + N
Once done, try to check the customer section if you can see the notes. If the issue persists, return to your default browser and perform a clear cache to refresh the system. However, if the error persists, try using other supported browsers.
Furthermore, did you receive an error message while attempting to log in? I'd appreciate it if you provide a screenshot of the error detail.
Additionally, if you'll want to check these resources to get more details about managing customers in QBO: