I'm dropping in to provide some insight on your connection issues. We were experiencing an intermittent server outage today (12-27-2018) that has since been resolved. However, to ensure a successful connection the next time you log in, I recommend clearing your browser's local cache files as a precautionary measure.
Services like QuickBooks Online store these files to keep you from having to load repetitive data and images each time you use them. These files can often become outdated or corrupted and require occasional clearing to retain utmost performance. You can accomplish this with the steps below corresponding to the browser/platform you're using:
There's also a detailed guide on deleting cache and temporary files here that can offer additional information. These instructions are all you'll need to get into your QuickBooks right away. Please keep in touch with me here should you have any additional questions or concerns, I'll have you covered. Thanks for coming to the Community, cheers to continued success.