When we built our first MVP, I was the technical cofounder and I did 99% of the work and I felt like I could take a break while the others pushed the app to users. As someone else mentioned, maybe your cofounder didn’t sign up to do this type of sales on top of his technical work?
Also, our mvp was embarrassingly bad, I knew it was so shit there wasn’t even a point giving it to my network and I didn’t want my name on something so poor. I had the mindset of “well I know what’s wrong already, I don’t need users to tell me”, so the test was inherently flawed and we basically only did it to reaffirm my position in which case I just needed to wait for my less experienced cofounders to catch up. Maybe this helps to explain your situation or maybe it’s nothing like it at all. Either way, just talk to them and relax a little, it’s a long journey
Team, expectations, vetting the idea, equity, I could actually go on for hours. 4 years later I’m still paying for it