Strike Back: The Complete Series (4 or 5 Seasons?)

[AZBrowncoat]

While perusing the digital code forum, I keep seeing listings for Strike Back: Season 4 (Final Season) or Strike Back: The Complete Series (4 Seasons) or similar postings which has me confused.

Wikipedia lists 5 seasons:
https://en.wikipedia.org/wiki/Strike_Back_(TV_series)

Amazon has a listing for:
Strike Back (Complete Series 1-5) - 14-DVD Box Set ( Strike Back (46 Episodes))

And yet the S:4 DVD release is also billed as the "Final Season".

I've been looking for a digital code for Strike Back: Season 5 but I'm puzzled because I'm seeing Seasons 1-4 being listed as "complete".

Was it the 2 year gap between S:4 & S:5 and the fact that S:5 hasn't been released digitally?

I haven't started watching the show yet and have S1-S:4 digitally already, so I'm wondering if there is any reason to continue looking for S:5?