Im stuck on version 4.4.2 and I cant update my Galaxy S5

[AC Question]

I got the phone online about a year ago and I have never been prompted to update the phone's software. I discovered that my outdated software is causing problems with other apps and now I want to update. The problem is that every time I go into my Settings and check About Device and have it Check for Updates it says its up to date which I know is not the case. I have tried also going into the Application Manager where I have Cleared the Data on Google Services Framework app and then also instructing it to Force Stop and then checked for new updates but with no success. The video that told me to do that step said it had to be done multiple times, I've only done it 3 times but I don't know if I should continue attempting that or do something else.