If different PDF viewers show different things, they are probably broken. Check with Adobe's reader (that one should be the gold standard), check with tools that do only PDF (or document) viewing, like on Linux xpdf(1) or evince(1). See what your (PDF) printer prints.
You might want to check if newer versions of the tools are available, and if they still misbehave.
Make a minimal example (LaTeX et al source, generated PDF) and report any bugs as appropiate.
\documentclass[twocolumn]{article}
\usepackage{stfloats}
\usepackage{graphicx}
\begin{document}
bla bla bla bla bla bla (text)
\begin{figure*}[t]
\centering
\includegraphics[width = 6 cm]{example-image-a}
\caption{Hi! I'm Figure A.}
\label{fig:figureA}
\end{figure*}
\begin{figure*}[b]
\centering
\includegraphics[width = 6 cm]{example-image-b}
\caption{Figure B, thats me!.}
\label{fig:figureB}
\end{figure*}
\def\a{bla bla bla bla bla bla (text)}
\a\a\a\a\a\a\a\a\a\a\a\a\a\a\a\a\a\a\a
\a\a\a\a\a\a\a\a\a\a\a\a\a\a\a\a\a\a\a
\a\a\a\a\a\a\a\a\a\a\a\a\a\a\a\a\a\a\a
zzz \a\a\a\a\a\a\a\a\a\a\a\a\a\a\a\a\a\a\a
\a\a\a\a\a\a\a\a\a\a\a\a\a\a\a\a\a\a\a
\a\a\a\a\a\a\a\a\a\a\a\a\a\a\a\a\a\a\a
\end{document}
Best Answer
You need to specify
[H]
like the code belowAdd
\usepackage{float}