Can you ensure that any packages are fully removed from your package management system. This is assuming you installed the dpkg version. Run the following:
If it returns any entries, e.g.
apt-cache search WowzaStreamingEngine
then make sure any instance is stopped and try removing them using dpkg like so:
# apt-cache search WowzaStreamingEngine
wowzastreamingengine-4.1.2 - Wowza Streaming Engine
wowzastreamingengine-4.1.1 - Wowza Streaming Engine
"Purge" will remove any lingering conf files etc as well as the core stuff.
dpkg --purge wowzastreamingengine-4.1.1
dpkg --purge wowzastreamingengine-4.1.2