What causes Error 44 when accessing an OpenEdge database?

What causes Error 44 when trying to access an OpenEdge database?

Error 44 indicates a version mismatch between the version read from the database Master Block and the utility or client version.  

How to determine the Progress version based on Error 44   
Is there a utility to display the Database Version?   

1.   More than one version of OpenEdge running on the same machine.

If more than one version of is OpenEdge installed, ensure the correct client version is trying to access the correct database version.

The client version will need to be changed to match:

• The Database Major Minor version to connect Self-Service, or
• The Database Major version or one Major version higher to connect Client-Server.

Error 44 connecting to the database   
Error 44 when runing a batch job to build indexes   

2   OS Copying the database from another machine.

When OS Copying a database ensure that either the database has been quieted beforehand with PROQUIET, or shutdown and the bi file truncated.
While copying the database files ensure that these are copied in their entirety

Error 44 accessing a database OS copied from one machine to another.   
Error 44 accessing the database after copying files from a different machine.   
PROUTIL conv910 fails with error 11114   

3.   Master Block Corruption

Database fails to migrate with conv tools error 1115  
Error 44 reports version 0 or another bogus version when trying to start the database    
Error 44 accessing a Restored Database  
Database crashed with version mismatch and block corruption errors 

4.   The filesystem has been infected by a Virus

AdminServer cannot be started due to virus   
Database corrupted by zepto virus   
Database broker fails to start database with error (44) due to Locky virus.   

5.    A Progress Defect

PROSTRCT builddb fails after conv1011 with errors 44 6070