I wanted to help you with this enquiry.
This to me seems like it might be a browser issue.
Chrome and FireFox are usually the best web browsers to use QuickBooks Online with.
I would recommend trying to log in using an incognito/private window, this will allow us to see whether it is a browser issue or not.
For Chrome press CTRL + SHIFT + N, for FireFox press CTRL + SHIFT + P to open up this type of window.
Go to qbo.intuit.com and log in from there.
Let me know if this doesn't work and we can continue troubleshooting from there.