Ideally should not have a problem with this piece of kit. The height bar should be spring loaded, it may be stiff if it has not been moved for a while. I have done thousands of 5.56x45 with mine and had no issues. Ir recently did some 762x51 and it needed a bit of cleaning first.

I know this may not help but you might try a full strip down, clean and re-assembly. Often, where a primer is anular crimped rather than staked, you will get small slivers of brass taken off that accumulate round the mandrel and the height bar. This may have jammed it.

Great piece of kit, all the CSR bods swear by them so you should be fine

(after thought, this is definately wrong if it is a current unit. Is it possible that the space bar is handed (can go in either way up but then wont raise up enough?). I cant believe a piece of kit made in the US wont deal with one of its most popular cases).