Also, unusual behavior, like missing client details in QBO, can be caused by issues in the web pages. Thus, you can try using a private window or incognito when accessing your account. This is because it doesn't store data in the cache which prevents unexpected QBO responses.
Depending on the browser you're using, you can use the following shortcut keys to access one:
Ctrl+ Shift + N for Google Chrome .
Ctrl + Shift + P for Mozilla Firefox and Microsoft Edge .
Command + Shift + N for Safari .
Once done, access the client details again. If it works fine this time, go back to your regular browser and clear your browser's cache to refresh the system. If the issue persists, you can use another supported browser instead.