Example of the error:

PROGRAM PLC_PRG
VAR
	arr1 : INT := [1,2,3,4,5,6];
END_VAR


--> C0074: Unexpected array initialisation
--> C0032: Cannot convert type 'Unknown type: [1,2,3,4,5,6]' to type 'INT'

Error correction:

Example:
arr1 : ARRAY [1..6] OF INT := [1,2,3,4,5,6];