There are two possible reasons why buttons and their functions end up grayed-out or disabled:
1) Upon opening a file, Delimit must complete a full file scan before all functions become enabled. If file scan is still running (or if it has been paused) the functions will be grayed-out/disabled until the scan completes. Allow the full scan to complete (or un-pause the scan) upon which the buttons will become enabled.
2) If file scan has completed, and the functions are still grayed-out, then you have likely edited or modified the file in one way or another, in which case you first need to save the file, to commit the changes, or close the file (without saving) and reopen it, before the functions will be enabled again.