The message you are getting means that you have an account that has been made inactive from your Chart of Accounts that still has a balance on it. This will typically affect your balance sheet. Because the account is not active then the funds within it are not accounted for in your balance sheet. Basically transactions have been entered that will not be accounted for.
The message will display the Account in question and balance that it has.
Steps you can take to investigate
First have a look at the account in question to understand what transactions have been loaded against it. If you make the account active once more and then run the Account Entries Report on it to see what the entries made against the account are you should have a better understanding of the transactions made to the account. Once you understand this you can work out how to deal with the balance before you make the account inactive again.
To make the account Active again go to your Chart of Accounts (Accounting > Accounts > Accounts List). You will need to go to the Master List of accounts to see all active and inactive account.
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Find the account that is listed in the Health Check message and click on it. Down the bottom of the screen will be a tick box for each division your Actionstep database has (most users will only have one division). Tick the box to make the account Active for that division.
Now the account is Active you can run the Account Entries Report on it (Reports > Accounting Reports > Account Entries Report). Make sure you run it for a large date period so that you can capture all the transactions that have been entered involving that account.
Now you are armed with information about this you need to decide if the account should be inactive (you can leave it in its current Active state) or if the transactions within in it should be accounted elsewhere. You may want to complete a General Ledger Journals to zero out this account then make it Inactive again.
We suggest you consult with your Accountant if you are unsure how to deal with this.