Is this an awkward ordering of words? (Cantonese)
機 is not the object, It is part of the verb phrase "開機" - "turn (machine/ device) on" 

Just like "吃飯" is a single verb phrase, where 飯 is not an object. 

The sentence is grammatical. Just too wordy. 

[(重新) + verb + (過)] is a set structure meaning [(from the start) + verb + (again)] e.g "重新做過" (from the start do it again)

The awkward part is 一次 is kind of redundant, "Do it again" already indicated "do it one more time" , you really don't need  to add "一次" (once) in this sentence.

Either 你要重新開過機 or 你要重新開一次機 (you have to start from the beginning and turn the device on again) would flow much more smoothly