A runtime error is a computer error that appears as the form of a message box consisting of a number code along with its corresponding definitions. After the runtime error message has been displayed & closed, the software that shows this error would normally close and/or freeze.

Run-time Error 21 – object variable or block variable not set!

Run-time error 21 Caution:

• You tried to use an object (connection, recordset, … ) without first declaring what it is.
• You don’t have ‘Option Explicit‘ at the top of your code module, to force a compile error if a object/variable is not declared & is used.

Windows System Error Codes:

• 21 (0×15 hex) – ERROR_NOT_READY – The device is not ready
• 0×21 (33 decimal) – ERROR_LOCK_VIOLATION – The process cannot access the file because another process has locked a portion of the file.

Get Startup-Mechanic tools to see what is starting and use diagnostic tools!.