Probably not, as long as you didn't personally guarantee any debts of the company's, or do anything to expose yourself to tort liability.
For a more meaningful response, you're best off taking all the corporation's formation and operational documents to a lawyer for review, and to discuss all the details of the situation.
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As long as you did not sign anything guaranteeing an obligation of the company (either when it was unincorporated or after it was incorporated) or sign anything as an individual (rather than as an officer of the company), you probably do not have personal liability. These are somewhat complex issues related to the content of any documents you signed on behalf of the company and how you signed those documents.
I would recommend that you speak with an attorney who can review all relevant documents and give you a more certain answer. From there, you would be in a better position to respond to the law firm requesting payment on the debt.
Ms. Koslyn and Ms. Olmon are correct in saying that you should contact counsel. You apparently did not formally undertake personal liability for any business debt. And the business undertook the liability before you arrived. However, when you arrived and for about six months, there was not yet any entity separate from human beings. You benefited from the going concern and its assets, including those from Vendor. You were leadership, a principal. You may have difficult burden of persuasion on your defense that only other principal(s) are liable.
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