No, it isn't offline. QuickBooks Online website is available anytime. I'll assist you in logging into your account.
Just to be sure, did you encounter any error when you try to sign in? Any information can help me find a solution to your problem.
QuickBooks Online loads and accesses the page using the cache and cookies of your browser. Sometimes all you need is a new start. Do a quick restart to clean the present status and issues in the background of your device.
If you still can't log in, you can try accessing your account using an incognito window. Then, log in using this direct link: QuickBooks Online account. Use the following shortcut keys below to open the incognito or private window: