The error “QuickBooks Cannot Communicate With the Company File” is a red flag that your software can’t reach the shared data. Common causes include:

QBDBMgrN not running

Damaged or missing .ND file

Incorrect hosting settings

Firewall or antivirus blocking ports

Corrupted company file or improper permissions
To fix the issue, start with the QuickBooks Tool Hub to scan and repair network settings. Recreate the .ND file by renaming the current one and reopening QuickBooks. Check that all users have the right file access permissions.
Also, make sure that only one computer (the server) is set to host multi-user access. If all else fails, try restoring a backup or contacting Intuit Support for deeper troubleshooting.

Company File Access Issue, QuickBooks Network Error, .ND File Fix, QuickBooks Tool Hub, Data File Communication Error

https://www.quickbooksupportnet.com/quickbooks-cannot-communicate-with-the-company-file/