Troubleshooting End{proof} Not Working: Possible Causes and Solutions

[tgt]

Why?

 

[cristo]

What are you talking about?

 

[Hootenanny]

Have you called the amsth package in the pre-amble? Note also that proof is an environment, so you would need to open the environment before closing it, i.e.

\begin{proof}

...

\end{proof}

Without seeing your latex code, it's difficult to diagnose your problem.