Mac OS X or newer is compatible with QuickBooks Online, Moogle07. Let me help you sort this out.
The Mac: OS X "El Capitan" 10.11 or newer is one of the minimum requirements. You should be able to log in without any issues.
I'd like to know more about this, though. What specific error did you encounter?
In the meantime, I'll share some steps that can fix unexpected issues in QuickBooks Online. You may be experiencing some browser hiccups. We'll perform some basic troubleshooting. Let's start with logging into your account through a private browser. It's the best place to identify web issues. These are the shortcut keys:
- Google Chrome: press Ctrl + Shift + N
- Mozilla Firefox: press Ctrl + Shift + P
- Safari: press Command + Shift + N
If you can log in successfully using the private browsing session, go back to your regular browser and clear its cache to refresh the program.
Also, you can use a different browser to narrow down the issue.
Feel free to get back to this thread with more information. We'll respond as soon as we can. Take care!