Error 301 and 6143.can't back up file. told to download company file diagnostics tool. cant find it.

A damage file component is one of the main reason why you're getting this error, jo.okumu. 

Prior from downloading the file doctor tool, you might want to ensure first your QuickBooks is updated. This is to make sure everything will go smoothly when running the tool.

Once done, you can check this out for steps on how to use and download file doctor: Fix company file and network issues.

If the issue continues, you can proceed to solution 2 and 3 in the article: Error when opening a company file or restoring a backup.

You always have a space in the Community, so please visit us again if you need anything else.

We Hope so that you have done successfully the troubleshooting of Error 301 and 6143.can't back up file. However in case it persists, So you can try the below given article link to know further advance troubleshooting.

Click Here.