I've been frustrated with this for quite some time - and no solutions from QB.  Here is what I have found that is the problem when I was having this: it's all about windows security credentials.  I had installed QB under an account with full admin rights.  I ran it that way for a while all all was OK.  I then switched my windows account to just a user and made one of my other accounts admin. I feel like it worked ok for a while and then all the sudden - broken.

I tried everything - but nothing worked until I did this:

1. create a new windows user account with basic admin rights (I called mine business)

2. Copy your QB file to a location that can be seen by that account

3. Open your file in that account

4. It should work

When QB tells you that you need an update, you will need to run the update software as an admin in that username account.  It's a little tricky.  I think I had to make that account an admin - run the software to get the update and then put it back to a limited user.

It feels like this is a major coding shortfall by qb and they won't tell you how to fix it unless you shell out hundreds of dollars in support fees.  They of course want you to upgrade to the newest qb because... it is a subscription model now - and you have to pay them every year for the software.  Stick with what you have and try what worked for me.

Good Luck!