I’m glad to offer my assistance with the 502 bad gateway error.
It’s a pretty simple fix. All you need to do is sign out of your QuickBooks, clear your Cache in the web browser, then sign back in. Your web browser stores data and after some time it needs to be cleared.
Here are some shortcuts to clear the browsing history.
Windows: Ctrl + Shift + Delete
Mac: Command + Shift + Delete
If you have any additional questions or concerns, feel free to contact me.