I invited my accountant using the invite facility but for some reason she can't access my accounts

Appreciate what you've done on your end, @ellismp. No worries. Let me guide you through the process. 

QuickBooks emails an invite to your accountant. The email has steps for how to connect to your accounts. We can check if the email expires and send another one. Otherwise, I'd suggest inviting an accountant again. 

Moreover, you can check this article to find out what happens when you invite your accountant: Add accountant users in QuickBooks Online.

However, if this continues, we can open an incognito window to prevent your browsing history from being saved. To determine if the issue is related to your browser, you can try doing this.

You can use the following keyboard shortcuts based on what type of browser you're using:

• Google Chrome: Ctrl + Shift + N
• Mozilla Firefox: Ctrl + Shift + P
• Microsoft Edge: Ctrl + Shift + P
• Safari: Command + Shift + N

If it works fine from there, we can go back to the regular browser and clear your cache. On the other hand, if the issue persists, you may use an alternative browser to access your QuickBooks Online account.

Additionally, I've included this article for you to check and learn what to do if invited users did not receive, or can't find, your email invitation to use QuickBooks Online: What to do if invited users did not receive your email invitation in QuickBooks Online. 

Please don't hesitate to click the Reply button if you need additional assistance managing user roles in QuickBooks Online. I'll keep an eye out for it. Keep safe.