What can I do when I can no longer pay my rent for my business because of no fault of my own?

It's not true to say that it was no fault of your own, by being self employed/ a director you were aware of the risks and should have taken adequate steps to mitigate those risks for example having savings and an investment portfolio if you are a sole trader and having sufficient liquidity if it is a limited company. If it is a limited company then if it cannot sustain it's costs then as a director you should put it into administration. If it was genuinely not your fault for example a client owes you money then while the aforementioned still holds true, you should threaten legal action to reclaim what is owed and if necessary goto court. however as this takes time it underscores the importance of having capital reserves.