Normalisation not available

On occassion after recording a track the normalistion feature is "greyed out" but after a while doing something else such as disarming the trcak or selecting another track, it reappears.
This has happened on single track and when recording multi tracks at once.

I am using a Digidesign 001 card with Reaper 4.15. This old card seems in every other respect to work superbly - 3 ms latency and Fx by the ton with no problems...

As I say the problem is mildly annoying as the time gap to enable the Normalisation can be a minute or so.

I could not find any other mention of this so maybe it's my card/computer combo or possible user ignorance.