I'll be glad to guide you through how fix this. You can download and run our QuickBooks Tool Hub. It has different tools that can help fix program and network related issues including unable to open company file. Let me guide you how to do it.
Additionally, here's a link that'll help you manage QuickBooks-related tasks. It has our QuickBooks topics with articles to guide you along: View all help for QuickBooks Desktop.
Let me know how it goes of the above recommendation don't help, I'm always here for you. Take care and have a good one.