Joe, by the sounds of it, you are going to need to descale that whole machine. You can get it working temporarily but it is only a matter of time before you are going to be shut down again. From my experience with the same machine you own, the biggest problem you will face for a descale is draining the boiler. Mine had no drain so you have to pull the end off with the heating element. You could do an inline descale if you use citric acid instead of sulphamic or other more rapidly acting acid. You would need to do a significant and repeated flush of the boiler though to get it all out.
Good luck.
Chris