Unable to open existing company file after desktop download

Activating QuickBooks Desktop (QBDT) 2016 will resolve with assistance from our experts, @SierraOne.

I'll ensure that you can open the 2016 QBDT version and the existing company file without delay. This way, you can get back where you left off. 

Due to the three-year support, you've come across a brick wall that prohibits self-reactivation. With this, I'd recommend contacting our Technical support to get this edition newly registered on a new computer. Also, our experts can help you activate your account. 

Here's how: 

1.  Go to this QBDT help link. 
2. Select your product and click Continue. 
3. Enter your concern in the box and tap Continue. 
4. Choose either Chat with us or Have us call you.  
5. Follow the on-screen instructions.

Make sure to contact them within business hours to ensure a swift response.

In regards to your company file, I agree with Fiat Lux - ASIA that you'll need to copy the file to your local machine. This way, you run the data seamlessly. 

Further, check out these articles below on how to fix activation code and company file problems in QuickBooks: 

• Fix activation, license, and product numbers errors
• Fix data damage on your QuickBooks Desktop company file

Add a response below if you have follow-up questions or need extra help handling your company file. I'm happy to assist you again. Take care, SierraOne.