A word for a failure to keep up-to-date

I'm trying to think if there's a word for a failure to keep up-to-date. For example, the British NHS's recent well-documented failure to maintain Windows XP, or a professional's failure to maintain Continuing Professional Development.

E.g.

"I'm not sure that your [delinquency] is our problem."

'Delinquency' may in fact be the best word, but I had in my mind something more akin to reprobation - I just can't quite put my finger on it, if indeed there is an 'it' to begin with.

Any thoughts?

obsolescence

The process or fact of becoming obsolete or outdated, or of falling into disuse

(Oxford English Dictionary)

The process of becoming obsolete or outdated and no longer used

(Oxford online dictionary)