SeaworthinessIll1950's journey

I recently found myself in a tough situation at a startup where I joined as a Performance Marketer back in August. The company is still in the process of developing an app, and my initial months were primarily spent onboarding—familiarizing myself with product documentation, crafting a marketing strategy, and setting up our marketing tools. Since the product hasn't launched yet, I haven't been able to execute any marketing campaigns or spend any budget on ads. In October, I contracted dengue fever, which forced me to take a week off for sick leave, followed by another week of working from home to recover. When I returned, I noticed a significant shift in the office dynamics. To my shock, I learned that the founder had been telling others that I was "not working well." Shortly after, HR sent me an email notifying me that I was being placed on a Performance Improvement Plan (PIP) starting this month. I feel completely blindsided by this decision. How can they assess my performance when I haven't even had the chance to launch a campaign or demonstrate my work? It seems like my medical leave may have triggered this response from the founder, and now they are using the PIP as a justification. I'm reaching out to see if anyone else has faced a similar situation at a startup. What are my options? Should I discuss this with HR and consider not signing the PIP? Any advice would be greatly appreciated.