There are distinct causes why QuickBooks won't open. To overcome the issue, you need to see the underlying reasons for the problem. You need to troubleshoot for the below conditions to comprehend the issue:
QuickBooks company file may be damaged
The company file must be corrupted.
Virus, malware, or trojan must have attacked your system. These malicious entities must have corrupted or damaged your files.
The same file must be shared or opened on a shared network.
You must be using the wrong methods to open specific files.
You must be using QuickBooks which must be incompatible with your operating system.