If you or the investor are officers or shareholders of the Corporation, you would be empowered to act on its behalf. Why did the landlord lock you out if Rent was not due again until May 1st? You need a business attorney for a brief consultation. The matter could probably be resolved with a single phone call from an attorney to the landlord. There may need to be an addendum made to the lease to reflect the free April rent.
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Your question has several facts that may or may not be relevant to your situation, such as the fact that one of the partners was arrested for embezzlement and that the investor never got a key. You don't mention if you were notified why the locks were changed or if you have had any communication with the landlord about this situation, so it's impossible to know the extent of your problem. I suggest that you attempt communication with your landlord through an attorney and try to work this out. There is no way of knowing whether there was some miscommunication or other facts entirely that resulted in the lockout.
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