。
I have no energy left.
Literal
Strength [subject-が] don't-come-out [polite-ません].
力が出ない ('strength does not come out') is a conversational way to express running out of energy or strength — more everyday than the formal alternative 力が尽きる ('strength is exhausted'). 出ません is the polite negative of 出る. Useful in talking about fatigue or illness.