Ex came back to me saying they wanted to date again, and then blocked me a few days later

A few days ago, my ex texted me saying that they still loved me, and that they wanted to get back together, however, they quickly changed their mind because they thought they were still not over another person they tried dating. Even though I thought we were still on good terms, a few days later, they blocked me out of nowhere. My question is, what could’ve caused them to block me, and should I try to reach out to them, or should I just move on and forget it ever happened?