I had the same problem with QB Desktop (Accountant 2018). I used the verify and rebuild utility tools, however, the result showed there was nothing wrong with my data file. Then I read another user about checking the item, COGS, etc. Thinking about that, I realized that the account I was trying to make active was a subaccount, and the main account was inactive. When I pulled up the main account, the inactive box was not grayed out, so I clicked the box and removed the "make inactive" check mark. After selecting OK, QB prompted me if I wanted to make the subaccounts active, and I said yes. Then, the inactive subaccount was active. If I answered no to making the subaccounts inactive, even though the main account was active, the subaccount was inactive, and the box was grayed out. So you must answer yes to make the subaccounts when you make the main account active.