Good morning, @dirk-rejuv-co-uk. 

I appreciate you coming to the QuickBooks Community with your question about an error message you're receiving. 

To clarify, what actions are you performing when receiving this error message? 

In the meantime, I recommend clearing your browser's cache and cookies to help eliminate this error that's occurring in the system. 

I'll be waiting for your response! 

Hello,

It is likely that QuickBooks assigned the wrong currency as your home currency during setup.

Please try the following steps.

1. Go to your Chart of Accounts. You will find that some accounts have a currency attached to them by default, and that is not likely the currency you want. If that is the case, then.

2. Go back to your currency setting and change your Home Currency to that currency shown in the Chart of Accounts, even if it is not your preferred currency. Click save and refresh the account. At this point, please don't touch multi-currency.

3. Go back to currency settings and change the Home Currency to your preferred currency, save and refresh.

4. Now you should be able to enable multi-currency.