\implies

[thegaryking]

\centernot doesn't work well with \implies for some reason. the slash is over on the left, a quarter way over (at least as part of the beamer package)

[davidcarlisle]

Please always include a proper test file, it looks OK to me

\documentclass{article}

\usepackage{centernot,amsmath}

\begin{document}

\[A \centernot\implies b\]
\[A \implies b\]

\end{document}

If there is a problem in beamer, you would need to make a suitable test and report there.

[u-fischer]

closing as not reproducible.